Question

the number of protons in the nucleus of an atom is called its
o a valence
o b none of these
o c mass number
o d isotope number
o e atomic number
question 12 (1 point)
the transition metal that has 24 electrons as a +3 ion is

blank 1:

Explanation:

First Question (Multiple Choice)

• Option a: Valence refers to the combining capacity of an atom, related to electrons in the outermost shell, not protons.
• Option b: Incorrect as option e is correct.
• Option c: Mass number is the sum of protons and neutrons in the nucleus.
• Option d: There is no "isotope number" defined as the number of protons; isotopes differ in neutron number.
• Option e: By definition, the atomic number of an atom is the number of protons in its nucleus.

Step1: Determine the number of protons

A + 3 ion means the atom has lost 3 electrons. If the ion has 24 electrons, the neutral atom has \(24 + 3=27\) electrons. In a neutral atom, the number of electrons equals the number of protons, so the atomic number (number of protons) is 27.

Step2: Identify the element

The element with atomic number 27 is cobalt (Co).

Answer:

e. atomic number

Second Question (Fill - in - the - Blank)