Question

a. complete the following sentences with the correct words.

1. protons are subatomic particles that have ______ electrical charges.
2. ______ are subatomic particles that have negative electrical charges.
3. ______ are subatomic particles that do not have any electrical charge.
4. the masses of subatomic particles are expressed in units called ______.
5. protons and neutrons both have masses equal to ______.
6. the atomic mass of the ______ is about 1/1836 the mass of a single proton.
7. the number of protons in an atoms nucleus or the number of electrons circling about it is called the atoms ______.
8. the ______ of an atom is the total number of protons and neutrons located in its nucleus.
9. there are many different kinds of atoms because their nuclei contain ______ numbers of protons.
10. the difference between an atoms atomic mass and its atomic number indicates how many ______ there are in the nucleus.
11. atoms of the same element that have different atomic masses are called ______.

b. complete the following table with the correct numbers.

element	atomic number	atomic mass	protons	neutrons	electrons
fluorine	9	19	______	______	______
gold	79	197	______	______	______
tin	50	119	______	______	______
uranium	92	238	______	______	______

Explanation:

Part A:

Step1: Recall proton charge property

Protons carry positive charge.

Step2: Recall negative subatomic particle

Electrons have negative electrical charge.

Step3: Recall neutral subatomic particle

Neutrons have no electrical charge.

Step4: Recall subatomic mass unit

Subatomic masses use atomic mass units.

Step5: Recall proton/neutron mass value

Protons/neutrons = 1 amu each.

Step6: Recall electron mass relative to proton

Electron mass ≈ 1/1836 of proton.

Step7: Recall proton/electron count term

Proton/electron count = atomic number.

Step8: Recall proton+neutron count term

Proton+neutron sum = atomic mass.

Step9: Recall proton count & atom identity

Different proton counts = different atoms.

Step10: Calculate neutron count formula

Neutrons = Atomic mass - Atomic number.

Step11: Recall same-element mass variants

Same element, different masses = isotopes.

Part B:

Step1: Protons = Atomic Number

Protons = Atomic Number, so copy atomic number value.

Step2: Electrons = Protons (neutral atom)

Electrons = Protons for neutral atoms, copy proton value.

Step3: Neutrons = Atomic Mass - Protons

Neutrons = Atomic Mass - Protons, calculate:

• Boron: $11 - 5 = 6$
• Fluorine: $19 - 9 = 10$
• Gold: $197 - 79 = 118$
• Tin: $119 - 50 = 69$
• Uranium: $238 - 92 = 146$

Answer:

Part A

1. positive
2. Electrons
3. Neutrons
4. atomic mass units (amu)
5. 1 atomic mass unit (amu)
6. electron
7. atomic number
8. atomic mass
9. different
10. neutrons
11. isotopes

Part B

Element	Atomic Number	Atomic Mass	Protons	Neutrons	Electrons
Fluorine	9	19	9	10	9
Gold	79	197	79	118	79
Tin	50	119	50	69	50
Uranium	92	238	92	146	92