fundamental particles

Question 1

what do the A, Z and X stand for in this:

A
X
Z

Answer 1

A = the mass number
Z = the atomic number 
X = the element

Question 2

What is the mass number?

Answer 2

The total number of protons and neutrons in the nucleus of one atom of an element

Question 3

What is the atomic number?

Answer 3

The number of protons in the nucleus of an atom

Question 4

Why is the number of protons and electrons the same?

Answer 4

because atoms are neutral and electrons have a negative charge and protons have a positive charge therefore the charges cancel each other out

Question 5

What is the relative charge on a proton, neutron and electron?

Answer 5

proton = postive 
neutron = neutral
electron = negative

Question 6

example:
Give the atomic number, mass number, proton number, electron number and neutron number of this element:

7
Li
3

Answer 6

atomic = 3
mass  = 7
proton = 3
electron = 3 
neutron = 7-3 = 4

Question 7

What is an ion?

Answer 7

An element that has different numbers of protons and electrons (but the proton number always stays the same and the electron number changes)

Question 8

If there is a + next to the element what does this mean?

Answer 8

The element has one less electron

Question 9

If there is a - next to the element what does this mean?

Answer 9

The element has one more electron

Question 10

example:
Given the atomic number, mass number, proton number, electron number and neutron number of this element:

7
Li +
3

Answer 10

atomic = 3
mass  = 7
proton = 3
electron = 2 --> because it has one less electron 
neutron = 7-3 = 4

Question 11

example:
Given the atomic number, mass number, proton number, electron number and neutron number of this element:

7
Li -
3

Answer 11

atomic = 3
mass  = 7
proton = 3
electron = 4 --> because it has one more electron 
neutron = 7-3 = 4

Question 12

What is the relative mass of a proton, neutron, and electron?

Answer 12

proton = 1
neutron = 1
electron = 1/2000 (negligible)

Question 13

What is an isotope?

Answer 13

Isotopes are atoms of the same elements that have the same number of protons but different numbers of neutrons. Therefore the atomic number is the same but the mass number is different

Question 14

what is the Ar?

Answer 14

Relative atomic mass
The average mass of an atom of an element relative to the mass of an atom of carbon 12, whose mass is defined as exactly 12

Question 15

what is the Mr?

Answer 15

Relative formula mass

The average mass of a molecule relative to the mass of an atom of carbon 12, whose mass is defined as exactly 12