Chemistry: Structure of atoms Vol2

The discovery of the atom is closely associated with the cathode ray experiment conducted by J.J. Thomson. In this experiment, Thomson demonstrated that cathode rays were composed of negatively charged particles (later named electrons), leading to the understanding of atomic structure.

The atom lost an electron, so it would become Na+Na+ (a cation), not N−N− (an anion)

The 3d orbitals are actually at a higher energy level than the 4s orbital. When filling orbitals, the 4s orbital is filled before the 3d orbitals because it has a lower energy level

Let's analyze the given information about the change in electronic configuration: Initial and Final Electronic Configurations. Initial State: 1s2-2s2-2p6-3s1. Final State: 1s2-2s2-2p6. Changes Observed. The element has lost the 3s1 electron during the chemical reaction. Evaluating the Statements, The element has become ionized. Correct: The loss of an electron indicates that the element has become ionized (specifically, it has formed a cation). The element gained an electron. Not Correct: The element did not gain an electron; it lost one electron. The element is likely to be a metal. Correct: Elements with a configuration ending in s1s1 are typically metals (like sodium), which tend to lose electrons easily. The new state is more stable than the initial state. Correct: The removal of the outermost electron results in a noble gas configuration, which is more stable

The proton was discovered by Eugen Goldstein through his work with canal rays, which are positively charged particles. Rutherford later confirmed the existence of protons in the nucleus.

Although James Chadwick is credited with the discovery of the neutron in 1932, Ernest Rutherford had previously theorized about the existence of a neutral particle in the nucleus.

The valency of an element is the number of hydrogen atoms that can combine with or replace one atom of the element. Valency of an element is also called the combining power of the element or the oxidation number of the element. It is the number of electrons in the outermost orbit of an atom Some elements have more than one valency and they are said to have variable valences

The empirical formula gives the simplest whole-number ratio of the elements in a compound. It indicates the relative proportions of each element, which is particularly useful for ionic compounds where the ratio of ions is essential. For example, the empirical formula for sodium chloride is NaCl, which shows the 1:1 ratio of sodium ions (Na⁺) to chloride ions (Cl⁻). Molecular formula: This specifies the actual number of each type of atom in a molecule but does not necessarily reflect the simplest ratio. The mole formula an atomic formula are not stand terms used in chemistry

According to the Pauli Exclusion Principle, no two electrons in an atom can have the same set of quantum numbers. This means that when filling the same orbital, the first electron will have one spin orientation (upward), and the second electron must have the opposite spin orientation (downward)

Mass Number: The total number of protons and neutrons in the nucleus (protons + neutrons)

Degenerate orbitals are those that have the same energy within a given principal energy level.

an atom that gains an electron becomes an anion, not a cation. Cations are formed when atoms lose electrons

The atom that gains the electron is commonly the metal.Explanation: This statement is incorrect because the atom that gains electrons is usually a nonmetal, which becomes negatively charged and forms an anion.

When an electron is removed from an atom, it becomes a positively charged ion (cation), not an anion. An anion is formed when an atom gains an electron.

Aufbau Principle: States that electrons fill orbitals starting from the lowest energy level to the highest. Pauli Principle: States that no two electrons in an atom can have the same set of four quantum numbers; an orbital can hold a maximum of two electrons with opposite spins. Hund's Principle: States that when electrons occupy degenerate orbitals, one electron enters each orbital until all orbitals are half-filled before pairing begins. Avogadro's Principle, on the other hand, relates to gases and states that equal volumes of gases, at the same temperature and pressure, contain an equal number of molecules. It does not govern the order in which electrons fill orbitals

To determine the number of protons and neutrons in the nucleus of element X, we need to analyze the information provided: Mass Number (A): The mass number of X is 24. This is the total number of protons and neutrons in the nucleus. Ion Charge: X2+ indicates that the element has lost 2 electrons. Since it contains 10 electrons, the number of protons must be: Number of protons=Number of electrons+Charge=10+2=12Number of protons=Number of electrons+Charge=10+2=12. Calculating Neutrons: Now, we can find the number of neutrons using the mass number: Neutrons=Mass Number−Number of Protons=24−12=12Neutrons=Mass Number−Number of Protons=24−12=12 Conclusion The nucleus of X will contain 12 protons and 12 neutrons. Or another way to look at it. To determine the number of electrons before becoming charged it is the number of electrons after becoming charged plus the number of charges so 10 + (+2)= 12. So the number of electrons before becoming charged is the number of protons in the nucleus. The mass number is number of protons plus neutrons

Atomic Number (Z): This represents the number of protons in the nucleus of an atom, which also equals the number of electrons in a neutral atom. The arrangement of these electrons, especially in the outermost shell (valence electrons), determines how an element reacts chemically

An atom with an atomic number of 12 is Magnesium (Mg). The electron configuration for Magnesium is1s2-2s2-2p6-3s2, This means Magnesium has 2 electrons in the 1s orbital, 2 electrons in the 2s orbital, 6 electrons in the 2p orbitals and 2 electrons in the 3s orbital. The 3s orbital can hold a maximum of 2 electrons. According to the Pauli exclusion principle, these two electrons will have opposite spins. The first electron in the 3s orbital will have an upward spin, and the second (final) electron will have a downward spin.Therefore, the final electron (the 12th electron) will have a downward spin in the 3s orbital.

An atom with an atomic number of 10 is Neon (Ne). The electron configuration for Neon is. 1s2-2s2-2p6. This means Neon has 2 electrons in the 1s orbital, 2 electrons in the 2s orbital and 6 electrons in the 2p orbitals (2px, 2py, 2pz). According to Hund’s rule and the Pauli exclusion principle, the electrons will fill the 2p orbitals as follows. The first three electrons will occupy the 2px, 2py, and 2pz orbitals with upward spins. The next three electrons will pair with the first three, having downward spins. Therefore, the last electron (the 10th electron) will have a downward spin in the 2pz orbital

when an electron gains energy, it moves to a higher energy level, not a lower one. Electrons emit energy when they drop to lower energy levels.

When an atom receives an electron, it becomes negatively charged and is referred to as an anion, not a cation. A cation is formed when an atom loses an electron.

The heating of metal foils indicates that cathode rays transfer energy when they collide with the metal. This energy transfer is a result of the kinetic energy of the particles in the cathode rays, which are electrons. While the statement "cathode rays conduct electricity" is somewhat indirect, it reflects the fact that these rays can transfer energy and interact with matter, demonstrating their energetic properties. Note: Cathode rays are composed of electrons, not neutrons or protons, and they do travel in straight lines unless deflected by an external force.

a larger principal quantum number (n) indicates a higher energy level and a greater average distance from the nucleus, not a lower energy level.

Let's analyze the given options regarding the atom and ion of sodium: Sodium Atom vs. Sodium Ion (Na⁺). Sodium Atom (Na): Atomic Number: 11 (has 11 protons and 11 electrons). Electron Configuration: 1s22s22p63s11s22s22p63s1. Sodium Ion (Na⁺): Formation: Formed when a sodium atom loses one electron. Protons: 11 (remains the same). Electrons: 10 (loses one electron) Options Analysis: The same chemical properties: Not Correct: Sodium (Na) and sodium ion (Na⁺) have different chemical properties due to the difference in their electron configurations. The ion is more stable and less reactive than the neutral atom. Electronic configuration: Not Correct: The electronic configuration of Na is 1s22s22p63s1, while for Na⁺ it is 1s22s22p6. They are different. Number of protons: Correct: Both the sodium atom and sodium ion have the same number of protons (11). Number of electrons: Not Correct: The sodium atom has 11 electrons, while the sodium ion has 10 electrons.

Aufbau principle says that orbitals are filled in order of increasing energy level.Pauli's principle says that an orbital can hold a maximum of two electrons, and they must have opposite spins. Hund's rule says that when electrons occupy orbitals of the same energy (degenerate orbitals), one electron enters each orbital until all orbitals are half-filled before pairing begins. The concept of electron capacity in orbitals is based on quantum mechanics rather than Dalton's atomic theory, which primarily dealt with the nature of atoms and their combinations. Dalton's atomic theory, proposed by John Dalton in the early 19th century, laid the foundation for modern chemistry. Here are the main postulates of Dalton's theory: 1)all matter is composed of indivisible atoms: 2) Atoms of the same element are identical: 3) Atoms combine in simple whole-number ratios: 4) In chemical reactions, atoms are rearranged: 5)Compounds are formed by the combination of different kinds of atoms:

Dalton did not discover the neutron; he proposed the atomic theory that included the existence of atoms but did not identify subatomic particles like neutrons.

Cathode rays, which are streams of electrons, travel in straight lines unless acted upon by an external magnetic or electric field. The statement about them running in curved paths is misleading without context regarding external forces.

Non-metallic is not a type of chemical combination. The other three (dative, ionic, and metallic) describe specific ways in which atoms combine. Dative bonds involve shared electrons where one atom donates both, ionic bonds involve electron transfer, and metallic bonds involve a sea of delocalized electrons

A binary compound is composed of exactly two different elements. Examples include sodium chloride (NaCl), which consists of sodium (Na) and chlorine (Cl), and water (H₂O), which consists of hydrogen (H) and oxygen (O)

The deflection of cathode rays in an electric or magnetic field demonstrates that they are charged particles. This is fundamental to understanding their nature as electrons.

Ionic (or electrovalent) bonding occurs when one atom transfers its valence electrons to another atom, resulting in the formation of ions that achieve stable electronic configurations (noble gas structure)

The idea that electrons circle the nucleus of an atom in a manner similar to planets orbiting the sun was proposed by Niels Bohr in 1913. This model is known as the Bohr model of the atom.

The electronic configuration is 1s2-2s2-2p6-3s2-3p6-4s2 (2,8,8,2)for calcium. Because it has the two electrons in the outermost shell (2,8,8,2) it is in group two of the periodic table and it has valency 2+ and its oxidation number is +2 because it will lose 2 electons to be able to combine with another element

The ability to cast shadow shows that the rays have mass

Reduction refers to the gain of electrons, while metals lose electrons during ionic bond formation. Hence, the metal is oxidized, not reduced

The principal quantum number, denoted by n, indicates the main energy level or shell of an electron in an atom.

The K shell corresponds to the principal quantum number n = 1. The value of n for the K shell is not 3; it is the first energy level.

Let's analyze the reaction between sodium ions (Na+) and chloride ions (Cl−) to determine which statement is not correct: Statements Analysis. The empirical formula is 2NaCl: Not Correct: The empirical formula for the ionic compound formed by sodium ions and chloride ions is simply NaCl. The ratio of sodium to chloride in the compound is 1:1, not 2:1. Sodium is the cation: Correct: Sodium ions (Na+) are positively charged, making sodium the cation. Chlorine is the anion: Correct: Chloride ions (Cl−) are negatively charged, making chlorine the anion. Sodium lost one electron to chlorine: Correct: Sodium loses one electron to form Na+, and chlorine gains that electron to form Cl−

An atom with a valency of +1 typically loses one electron, not gains or shares it, to achieve a noble gas configuration

The ability of cathode rays to cause small wheels to rotate indicates that these rays possess both mass and momentum, allowing them to exert force on the wheels.

The atom has one valence electron in the outer shell (3rd shell), so its electrovalency is +1, not +2

This statement is incorrect because protons are significantly more massive than electrons. A proton has about 1836 times the mass of an electron.

The cathode ray experiment revealed that the rays were composed of electrons, which are negatively charged particles.

Oxidation: This process involves the loss of electrons. In this reaction, calcium (Ca) is losing 2 electrons to form the calcium ion (Ca²⁺). Reduction: This process involves the gain of electrons. Since calcium is losing electrons, it is not a reduction reaction. Electronic Reaction: This term is not commonly used in chemistry to describe oxidation or reduction processes. Empirical Reaction: This term typically refers to a reaction that describes the simplest whole-number ratio of elements in a compound, not applicable here

The correct conclusion is that cathode rays are negatively charged because they are attracted to the positive plate of the electric field. This indicates that the rays consist of negatively charged particles (electrons).

The isotopes contribute fractions that make up the mean atomic mass. To find the percentage composition of the isotope of chlorine with a mass number of 35, we can use the formula for the weighted average of the isotopes. Let's denote: x: the fraction of the isotope with mass 35. 1−x: the fraction of the isotope with mass 37. Mean atomic mass =35.5. So (35x)+ [(1-x)37]= 35.5. and 35x+ [37-37x]=35.5 and 35x-37x+37= 35.5 and 37-2x=35.5 . When we re arrange 2x=1.5 then X=1.5/2=0.75

This statement is incorrect because the s sublevel has 1 orbital (which can hold 2 electrons). The p sublevel has 3 orbitals, the d sublevel has 5 orbitals, and the f sublevel has 7 orbitals.

J.J. Thomson discovered the electron in 1897 through his experiments with cathode rays. He demonstrated that cathode rays were composed of negatively charged particles, which he named electrons. This discovery was crucial in the development of atomic theory and our understanding of atomic structure.

The azimuthal quantum number (l) determines the shape of the orbital and describes the subshells (s, p, d, and f). The magnetic quantum number (m) describes the orientation of the orbitals within those subshells.

Metals typically lose electrons during chemical reactions to form cations. Nonmetals, on the other hand, tend to gain electrons