Question

1. the atomic number tells you the number of __________ in one atom of an element. it also tells you the number of ________ in a neutral atom of that element. the atomic number gives the “identity “of an element as well as its location on the periodic table. no two different elements will have the ______ atomic number.
2. the ______________________ of an element is the average mass of an element’s naturally occurring atoms, or isotopes, taking into account the __________________ of each isotope.
3. the __________ of an element is the total number of protons and neutrons in the __________ of the atom.
4. the mass number is used to calculate the number of __________________ in one atom of an element. in order to calculate the number of neutrons you must subtract the ________________ from the __________________.
5. give the symbol and number of protons in one atom of:

lithium __________________ bromine __________________
iron __________________ copper __________________
oxygen __________________ mercury __________________
arsenic __________________ helium __________________

Explanation:

1. The atomic number is equal to the number of protons in an atom. In a neutral atom, it is also equal to the number of electrons. Each element has a unique atomic number.
2. The atomic mass of an element is the weighted - average mass of its naturally - occurring isotopes, where the weights are the relative abundances of the isotopes.
3. The mass number of an element is the sum of protons and neutrons in the nucleus of an atom.
4. The mass number is used to calculate the number of neutrons. The number of neutrons = mass number - atomic number.
5. We use the periodic table to find the symbol and number of protons (equal to the atomic number) for each element.

Answer:

1. Protons; Electrons; Same
2. Atomic mass; Relative abundances
3. Mass number; Nucleus
4. Neutrons; Atomic number; Mass number
5. Lithium: Li, 3; Bromine: Br, 35; Iron: Fe, 26; Copper: Cu, 29; Oxygen: O, 8; Mercury: Hg, 80; Arsenic: As, 33; Helium: He, 2