Question

multiple choice
identify the choice that best completes the statement or answers the question.

1. the atomic number of an element is the total number of which particles in the nucleus?

a. neutrons
b. protons
c. electrons
d. protons and electrons

1. an element has an atomic number of 76. the number of protons and electrons in a neutra

element are ___.
a. 152 protons and 76 electrons
b. 76 protons and 0 electrons
c. 38 protons and 38 electrons
d. 76 protons and 76 electrons

1. the sum of the protons and neutrons in an atom equals the ___.

a. atomic number
b. nucleus number
c. atomic mass
d. mass number

1. what does the number 84 in the name krypton - 84 represent?

a. the atomic number
b. the mass number
c. the sum of the protons and electrons
d. twice the number of protons

1. all atoms of the same element have the same ___.

a. number of neutrons
b. number of protons
c. mass numbers
d. mass

1. isotopes of the same element have different

a. numbers of neutrons.
b. numbers of protons.
c. numbers of electrons.
d. atomic numbers.

1. isotopes of the same element have different

a. positions on the periodic table.
b. chemical behavior.
c. atomic numbers.
d. mass numbers.

Explanation:

1. The atomic number is defined as the number of protons in an atom's nucleus. Neutrons (a) are part of the nucleus but not what the atomic number counts. Electrons (c) are outside the nucleus. Protons and electrons (d) is incorrect as electrons are not in the nucleus for atomic number definition.
2. For a neutral atom, the number of protons equals the atomic number and the number of electrons (to balance charge). So with atomic number 76, protons = 76 and electrons = 76. Option a has wrong proton - electron count. Option b has 0 electrons (not neutral). Option c has wrong proton number.
3. The mass number is the sum of protons and neutrons in an atom. Atomic number (a) is just protons. "Nucleus number" (b) is not a standard term. Atomic mass (c) is a weighted average for an element's isotopes, not for a single atom.
4. In the notation like krypton - 84, the number (84) represents the mass number. Atomic number (a) would be a different value (for krypton, atomic number is 36). Sum of protons and electrons (c) for neutral krypton would be 36 + 36=72 (not 84). Twice the number of protons (d) for krypton would be 72 (36*2) not 84.
5. All atoms of the same element have the same number of protons (by definition of an element). They can have different neutrons (so a is wrong), different mass numbers (so c is wrong as mass number = protons + neutrons), and different masses (d, as mass depends on isotopes).
6. Isotopes of the same element have the same number of protons (so b is wrong) and same atomic number (so d is wrong, since atomic number = number of protons). For neutral atoms, same number of electrons (so c is wrong). They have different numbers of neutrons.
7. Isotopes of the same element have the same atomic number (so c is wrong) and thus the same position on the periodic table (so a is wrong). They have very similar chemical behavior (so b is wrong as chemical behavior is mainly determined by electrons, and same number of electrons for neutral isotopes). They have different mass numbers (mass number = protons + neutrons, and neutrons differ in isotopes).

Answer:

1. B. protons
2. D. 76 protons and 76 electrons
3. D. mass number
4. B. the mass number
5. B. number of protons
6. A. numbers of neutrons
7. D. mass numbers