Question

question 16
0.25 pts
atomic mass is determined by the number of:

• protons and electrons.
• neutrons and electrons.
• neutrons, protons, and electrons.
• protons and neutrons.

question 17
0.25 pts
in the presence of a base, red litmus paper will:

• stay red.
• turn blue.
• turn green.
• turn yellow.

question 18
0.25 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.

Explanation:

Question 16

Atomic mass is the sum of protons and neutrons in an atom. Electrons have negligible mass, so they don't contribute significantly to atomic mass. So the correct option is the one with protons and neutrons.

Litmus paper is an indicator. Red litmus paper turns blue in the presence of a base (alkaline conditions), while blue litmus paper turns red in acid.

Step1: Determine Protons

Atomic number = number of protons. Given atomic number is 12, so protons = 12.

Step2: Determine Neutrons

Atomic mass ≈ protons + neutrons. So neutrons = atomic mass - protons = 25 - 12 = 13.

Step3: Determine Electrons

A +2 charge means the atom has lost 2 electrons. Neutral atom has electrons = protons = 12. So electrons = 12 - 2 = 10.

Answer:

D. protons and neutrons.

Question 17