3 - Atomic Structure

Question 1

When did John Dalton publish his ideas about the atom?

Answer 1

1803

Question 2

Describe how John Daltons idea of the atom looked like:

Answer 2

Solid ball

Question 3

State some ideas in regards John Dalton’s atomic theory:

Answer 3

• Atoms cannot be broken down into anything simpler
• The atoms of a given element are identical to each other
• The atoms of different elements are different from one another
• During chemical reactions atoms rearrange to make different substances

Question 4

What did Daltons theory help to explain?

Answer 4

The properties of matter

Question 5

What is the relative charge of a Proton?

Answer 5

+1

Question 6

When was the electron discovered? And by who?

Answer 6

In 1897 by JJ Thompson

Question 7

What model did JJ Thompson propose?

Answer 7

Plum pudding model

Question 8

Describe how the plum pudding model looked like:

Answer 8

An atom is a sphere of positive charge, with negatively charged electrons scattered in it

Question 9

Explain how Ernest Rutherford discovered the nuclear atom:

Answer 9

He did the gold foil experiment.

He directed a beam of alpha particles at a very thin gold foil in a vacuum

Question 10

What observations did Rutherford see during the gold foil experiment?

Answer 10

• Most alpha particles went straight through
• A small number of alpha particles were being deflected at large angles
• There were a very small number of alpha particles coming straight back

Question 11

What does a small number of alpha particles were deflected @ large angles show in the gold foil experiment?

Answer 11

There is a concentration of positive charge in the atom

Question 12

What does a small number of alpha particles were coming straight back show in the gold foil experiment?

Answer 12

The positive charge and mass are concentrated in a tiny volume in the atom (the nucleus)

Question 13

What does most of the alpha particles going straight through show in the gold foil experiment?

Answer 13

Evidence for the atom being mostly empty space

Question 14

Why is it important that Rutherford conducted the gold foil experiment in a Vacuum?

Answer 14

So any deflection of the alpha particles would only be because of collisions with the gold foil.
And not due to deflections off anything else

Question 15

Who confirmed that the rearranged order of elements is correct?

Answer 15

Henry Moseley

Question 16

Describe the structure of an atom:

Answer 16

A nucleus containing protons and neutrons, surrounded by electrons in shells

Question 17

What is the relative charge of a Proton?

Answer 17

+1

Question 18

What is the relative charge of a Electron?

Answer 18

-1

Question 19

What is the relative charge of a Neutron?

Answer 19

0

Question 20

What is the relative mass of a Proton?

Answer 20

1

Question 21

What is the relative mass of a Electron?

Answer 21

1/2000
or
1/1835

Question 22

What is the relative mass of a Neutron?

Answer 22

1

Question 23

Where is most of the mass in an atom concentrated?

Answer 23

The Nucleus

Question 24

What does the term Mass number mean?

Answer 24

The total number of protons and electrons in the nucleus of an atom

Question 25

What do we measure the *mass of atoms* relative to?

Answer 25

An atom of carbon 12

Question 26

What's the relative mass of Helium-4?

Answer 26

4

Question 27

What's the relative mass of magnesium?

Answer 27

24

Question 28

What does the term **Isotopes** mean?

Answer 28

Different atoms of the same element containing the **same number of protons** but **different numbers of neutrons** in their nuclei

Question 29

Describe the size of the nucleus of the atom:

Answer 29

Very small compared to the overall size of the atom

Question 30

What is an **atomic number**?

Answer 30

The number of protons in the nucleus of an atom

Question 31

What is the **atomic number** also known as?

Answer 31

Proton number

Question 32

Label which is the following: - Mass number - Atom symbol - Atomic number

Answer 32

Question 33

What is **Nuclear fission**?

Answer 33

When the nucleus of a large atom splits into 2 smaller nuclei

Question 34

What is **Relative atomic mass**?

Answer 34

The mean mass of an atom of an element compared with Carbon-12

Question 35

What does RAM stand for?

Answer 35

Relative atomic mass

Question 36

What does RAM take into account?

Answer 36

All the isotopes of the element + amounts of each

Question 37

How do you calculate **RAM** using relative masses and the abundances of its isotopes?

Answer 37

Question 38

Calculate the RAM of an element:

Answer 38

Question 39

Why does the existence of isotopes results in relative atomic masses of some elements not being whole numbers?

Answer 39

RAM is the MEAN mass of an atom. It takes into account all the isotopes of the elements + amounts Therefore, RAMs are not whole numbers, most values are commonly rounded to whole numbers

Question 40

What is **mass number**?

Answer 40

The total number of protons and neutrons

Question 41

Where is most of the **mass** in an atom *concentrated* in?

Answer 41

The Nucleus

Question 42

Explain why *atoms* are neutral?

Answer 42

They always have the same number of protons and electrons ---> Charges cancel out