3.1 - Electron Theory - 3q

Question 1

What does the term matter mean?

Answer 1

Matter is anything that has weight and occupies space

Question 2

How many elements have been idenified and how many of these occur in nature?

Answer 2

There are 118 elements that have been identified

Of these, only 94 occur in nature, these are called the natural elements

Question 3

In terms of electron theory, what is the weight and location of each sub atomic particle?

Answer 3

Nuetrons and protons have approximately the same weight and size

They are much heavier than electrons meaning the weight of an atom is determined primarily by the number of protons and neutrons in the nucleus.

Question 4

What is special about the Hydrogen atom?

Answer 4

One electron orbiting one proton

Contains no neutrons

Question 5

What is meant by an atom that is in its normal balanced or neutral state

Answer 5

The electrons are equal to the number of protons

Question 6

What is Ionization

Answer 6

Ionization is the process by which an atom or a molecule acquires a negative or positive charge by gaining or losing electrons to form an ion

Question 7

Why does an electron keep orbiting a nuclues and not fly off?

Answer 7

The centrifugal force of the electron that thrusts it away from the nuclues is exactly offset by the attraction of the protons in the nucleus.

Question 8

What is the name given to the outermost shell of an atom?

Answer 8

The outer shell is called the valence shell and the electrons in this shell are called valence electrons

Question 9

What are inert gases?

Answer 9

Inert gases have 8 electrons in their valence shell. The valence shell is completely filled and as a result these elements are so stable that they resist any sort of chemical activity. They will not even combine with other elements to form compounds. They are also reluctant to give up any electrons.

Examples: Neon, Argon, Krypton, Xenon, Radon

Question 10

What are two materials that are semiconductors?

Answer 10

4 electrons (shell half full)

Germanium

Silicon

Question 11

What is the definition of matter?

Answer 11

Matter describes everything that has weight and occupies space.

Question 12

Name the components of an atom?

Answer 12

Electron, proton and neutron (except Hydrogen)

Question 13

What is the only element that does not contain a neutron?

Answer 13

Hydrogen

Question 14

Which is the lightest sub-atomic particles

Answer 14

Electron

Question 15

What is the most complez element found in nature?

Answer 15

Uranium

92 electrons, 92 protons

146 neutrons

Question 16

An atom is electrically neutral. What does this mean in terms of its sub-atomic particles?

Answer 16

The number of protons in the atom is equal to the number of electrons in it

Question 17

What is an Ion

Answer 17

An ion is an atom that is positively or negatively charged i.e not in its natural state

Question 18

How is a negative Ion formed

Answer 18

Surplus of electrons

Question 19

What can cause atoms to loose electrons

Answer 19

The outermost electrons (valence electrons) are loosely bound to the nucleus. Hence, these electrons keep moving from one atom to another (direction of current)

Question 20

Which electrons are easily freed and used for electrical conduction?

Answer 20

Electrons in the outermost shell (valence shell)

Question 21

An element whose valence shell is filled is called what?

Answer 21

Insulator

Question 22

How do you categorise the following amount of electrons in the outermost shell>

1 - 3

4

5-8

Answer 22

1 - 3 = Conductor

4 = Semiconductor

5 - 8 = Insulator

Question 23

A substance with a large number of free electrons is called what?

Answer 23

Conductors

Question 24

What is a compound?

Answer 24

A compound is composed of two or more elements

Question 25

Define the following:

Atomic Number

Atomic Weight

Answer 25

Atomic number is the number of protons in the nucleus of an atom

Atomic weight - total mass/weigth of an atom

Question 26

Give three examples of conductor, insulator and semiconductor

Answer 26

Conductor: Tungsten, Aluminium, Gold, Copper, Silver

Semiconductor: Germanium, Silicon

Insulator: Teflon, Fused Quartz, Wood (dry), air, hand rubber, glass, plastic and paper (dry)

Question 27

Define Ionization

Answer 27

Ionization is the process by which an ato or a molecule acquires a negative or positive charge by gaining or losing electrons to form ions