Answer:
protons plus neutrons
Explanation:
An atom consist of electron, protons and neutrons. Protons and neutrons are present with in nucleus while the electrons are present out side the nucleus.
All these three subatomic particles construct an atom. A neutral atom have equal number of proton and electron. In other words we can say that negative and positive charges are equal in magnitude and cancel the each other. For example if neutral atom has 6 protons than it must have 6 electrons.
The sum of neutrons and protons is the mass number of an atom.
Mass number = number of protons + number of neutrons
while the number of protons or number of electrons is the atomic number of an atom.
The question is incomplete, here is the complete question.
A chemist prepares a solution of copper(II) fluoride by measuring out 0.0498 g of copper(II) fluoride into a 100.0mL volumetric flask and filling the flask to the mark with water.
Calculate the concentration in mol/L of the chemist's copper(II) fluoride solution. Round your answer to 3 significant digits.
<u>Answer:</u> The concentration of copper fluoride in the solution is 
<u>Explanation:</u>
To calculate the molarity of solute, we use the equation:

We are given:
Given mass of copper (II) fluoride = 0.0498 g
Molar mass of copper (II) fluoride = 101.54 g/mol
Volume of solution = 100.0 mL
Putting values in above equation, we get:

Hence, the concentration of copper fluoride in the solution is 
1)
a)
D = 0.79 g/cm³ m = 85.1 g
D = m / V
0.79 = 85.1 / V
V = 85.1 / 0.79 => 107.72 cm³
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b) D = m / V
0.79 = m / 125
m = 0.79 x 125 => 98.75 g
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hope this helps!
Electrons are both gained and lost.