Midterm 2 Atom/Periodic Table

Which statement describes the general trends in electronegativity and first ionization energy as the elements in Period 3 are considered in order from Na to Cl?

• Electronegativity increases, and first ionization energy decreases.

• Electronegativity decreases, and first ionization energy increases.

• Electronegativity and first ionization energy both increase.

• Electronegativity and first ionization energy both decrease.

Answer explanation

As you move from Na to Cl in Period 3, electronegativity and first ionization energy both increase due to increasing nuclear charge and decreasing atomic radius, making it harder to remove an electron and attracting electrons more strongly.

Which electron configuration represents the electrons in an atom of Ga in an excited state?

• 2-8-17-3

• 2-8-17-4

• 2-8-18-3

• 2-8-18-4

Answer explanation

Gallium (Ga) has an atomic number of 31, with a ground state configuration of 2-8-18-3. In an excited state, one electron can be promoted to a higher energy level, resulting in configurations like 2-8-17-4 or 2-8-18-3.

Which notations represent different isotopes of the element sodium?

• ³²S and ³⁴S

• S²⁻ and S⁶⁺

• Na⁺ and Na⁰

• ²²Na and ²³Na

Answer explanation

The correct choice is \(^{22}Na\) and \(^{23}Na\) as they represent isotopes of sodium, differing in neutron number. Other options either refer to different elements or charge states, not isotopes.

Two forms of solid carbon, diamond and graphite, differ in their physical properties due to the differences in their

• atomic numbers

• crystal structures

• isotopic abundances

• percent compositions

Answer explanation

Diamond and graphite are both forms of carbon, but they have different crystal structures. This difference in arrangement of carbon atoms leads to their distinct physical properties, making 'crystal structures' the correct choice.

The atomic mass of magnesium is the weighted average of the atomic masses of

• all of the artificially produced isotopes of Mg

• all of the naturally occurring isotopes of Mg

• the two most abundant artificially produced isotopes of Mg

• the two most abundant naturally occurring isotopes of Mg

Answer explanation

The atomic mass of magnesium is calculated as the weighted average of all naturally occurring isotopes of Mg, reflecting their relative abundances, not just the artificially produced ones or a limited selection.

When an excited electron in an atom moves to the ground state, the electron

• absorbs energy as it moves to a higher energy state

• absorbs energy as it moves to a lower energy state

• emits energy as it moves to a higher energy state

• emits energy as it moves to a lower energy state

Answer explanation

When an excited electron moves to a lower energy state (ground state), it releases energy in the form of light or heat. Therefore, the correct choice is that the electron emits energy as it moves to a lower energy state.

Compared to the charge of a proton, the charge of an electron has:

• a greater magnitude and the same sign

• a greater magnitude and the opposite sign

• the same magnitude and the same sign

• the same magnitude and the opposite sign

Answer explanation

The charge of a proton is +1, while the charge of an electron is -1. They have the same magnitude (1 unit of charge) but opposite signs, making the correct answer 'the same magnitude and the opposite sign'.

Given the bright-line spectrum of a mixture formed from two of these elements: Which elements are present in this mixture?

• A and D

• A and X

• Z and D

• Z and X

Answer explanation

The bright-line spectrum indicates specific wavelengths emitted by elements. The presence of lines corresponding to elements A and D confirms they are in the mixture, while the absence of lines for Z and X rules them out.

Which ion has the smallest radius?

• O²⁻

• S²⁻

• Se²⁻

• Te²⁻

Answer explanation

O²⁻ has the smallest radius because it has the highest effective nuclear charge relative to its size, leading to a stronger attraction between the nucleus and the electrons, thus pulling them closer compared to S²⁻, Se²⁻, and Te²⁻.

Which term represents the attraction one atom has for the electrons in a bond with another atom?

• electronegativity

• electrical conductivity

• first ionization energy

• mechanical energy

Answer explanation

Electronegativity is the term that describes the attraction an atom has for the electrons in a bond with another atom. It indicates how strongly an atom can attract bonding electrons.