Question

1. the nucleus of an atom consists of 8 protons and 6 neutrons. the total number of electrons present in a neutral atom of this element is a. 6 b. 2 c. 8 d. 14 2. isotopes of the same element must have the same a. atomic number b. mass number c. number of nucleons d. number of neutrons 3. if x is the symbol of an element, which pair correctly represents isotopes of x? a. $_{64}^{158}x$ and $_{64}^{158}x$ b. $_{158}^{64}x$ and $_{64}^{158}x$ c. $_{64}^{158}x$ and $_{64}^{159}x$ d. $_{64}^{158}x$ and $_{65}^{158}x$ 4. what is the net charge of an ion that consists of 10 electrons, 11 protons, and 12 neutrons? a. $1^{+}$ b. $2^{+}$ c. $1^{-}$ d. $2^{-}$ 5. the characteristic bright - line spectrum of an element is produced when electrons a. are given off as beta particles b. are gained from another atom c. move to higher energy levels d. fall back to lower energy levels 6. a $ca^{2 + }$ ion differs from a $ca^{0}$ atom in that the $ca^{2 + }$ ion has a. more protons b. fewer protons c. more electrons d. fewer electrons 7. which statement best describes the nucleus of an aluminum atom? a. it has a charge of + 13 and is surrounded by total of 10 electrons. b. it has a charge of + 13 and is surrounded total of 13 electrons. c. it has a charge of - 13 and is surrounded total of 10 electrons. d. it has a charge of - 13 and is surrounded total of 13 electrons.

Explanation:

1. In a neutral atom, the number of electrons equals the number of protons. Here, there are 8 protons, so there are 8 electrons.
2. Isotopes of the same element have the same atomic number (number of protons).
3. Isotopes have the same atomic number (subscript) but different mass numbers (superscript).
4. Net charge = number of protons - number of electrons. \(11 - 10=1^{+}\).
5. Bright - line spectra are produced when electrons fall back to lower energy levels and release energy.
6. A \(Ca^{2 +}\) ion has lost 2 electrons compared to a neutral \(Ca\) atom.
7. An aluminum atom (\(Al\)) has an atomic number of 13 (13 protons, so nucleus charge \(+ 13\)) and in a neutral atom, the number of electrons equals the number of protons (13 electrons).

Answer:

1. C. 8
2. A. atomic number
3. C. \(_{64}^{158}X\) and \(_{64}^{159}X\)
4. A. \(1^{+}\)
5. D. fall back to lower energy levels
6. D. fewer electrons
7. B. It has a charge of \(+13\) and is surrounded by a total of 13 electrons.