Question

question 7
1 pts
a magnesium atom has an atomic number of 12, an atomic mass of 25, and a +2 charge. this atom would contain ___ protons, _ neutrons, and ___ electrons.
12; 25; 2
12; 13; 14
12; 13; 10
not enough information is given to answer the question.

question 8
1 pts
an example of an element would be:
ne.
co₂.
c₆h₁₂o₆.
h₂o.

question 9
1 pts
carbon has an atomic number of 6. the number of electrons found in the first shell is:
two.
four.
six.
eight.

Explanation:

Question 7

Step1: Determine number of protons

The atomic number is equal to the number of protons. Given atomic number of magnesium is 12, so number of protons = 12.

Step2: Calculate number of neutrons

Atomic mass = number of protons + number of neutrons. So number of neutrons = atomic mass - number of protons. Given atomic mass = 25 and number of protons = 12, then number of neutrons = 25 - 12=13.

Step3: Calculate number of electrons

A +2 charge means the atom has lost 2 electrons. A neutral magnesium atom (with atomic number 12) has 12 electrons. So the ion has 12 - 2 = 10 electrons.

An element is a pure substance made of only one type of atom. Ne (neon) is an element. $CO_2$, $C_6H_{12}O_6$ and $H_2O$ are compounds made of different types of atoms.

The first electron - shell can hold a maximum of 2 electrons for any atom.

Answer:

12; 13; 10

Question 8