Topic 1 - Atoms, Molecules, Isotopes and Ions

Question 1

All the different substances in the world are made from fundamental materials called_______________

Answer 1

Elements

Question 2

What is an element?

Answer 2

An element is a:

• substance
• which cannot be split into 2 or more simpler substances
• by chemical means.

Question 3

How is every element unique?

Answer 3

Because every element has its own name and symbol.
Eg. Lithium = Li,
Magnesium = Mg

Question 4

All elements are made of many small particles called:

Answer 4

ATOMS

Question 5

In any one element, all the atoms are _______________.

The atoms of each element are unique because ___________________.

Answer 5

In any one element, all the atoms are identical to each other, but different from all other elements (in size and mass).
Each element has its own type of atoms.

Because the atoms of each element have a different size and mass from the other elements.

Question 6

What is an Atom?

Answer 6

An atom is the SMALLEST particle of an element.
It has the symbol of the element.

Question 7

How do you represent Atoms?

Answer 7

1. Circles (different size and symbols)
2. Ball and stick modles - spheres connected by sticks

Question 8

How can you see an atom?

Answer 8

Using an electronic microscope.

Question 9

What are the particles in an Atom?

Answer 9

Sub-atomic particles called:

1. Protons;
2. Neutrons; and
3. Electrons

Question 10

What do Protons and Neutrons make up?

Answer 10

The Nucleus of the Atom.

Question 11

What is the symbol, charge and relative mass of a proton?

Answer 11

Symbol = p
Relative Electric Charge = +1
Relative mass = 1

Question 12

What is the symbol, charge and relative mass of a Neutron?

Answer 12

Symbol = n
Relative Electric Charge = 0
Relative mass = 1

Question 13

What is the symbol, charge and relative mass of an Electron?

Answer 13

Symbol = e
Relative Electric Charge = - 1
Relative mass = 1/1840

Question 14

Every element has its own Atomic Number and Mass Number.

How do you indicate the Atomic Number and

Mass Number of an element?

Answer 14

Question 15

What is an Mass Number of an element?

Answer 15

Mass Number =

Total Number of

Protons + Neutrons

Question 16

What is an Atomic Number of an element?

Answer 16

Atomic Number = Number of protons

Notes:

1. It is the proton number that identifies an element.
2. The number of protons differentiates atoms of one element from the atoms of another element.
3. The elements in the Periodic Table are arranged in order of the number of Protons.
4. The number of protons in the atoms of an element is FIXED.
5. A change in the number of protons will change the element.

Question 17

How do you find the number of electrons in an element?

Answer 17

The number of electrons = The number of Protons = Atomic Number (bottom)

So the number of electrons = Atomic Number also

Question 18

How do you find the number of neutrons in an element?

Answer 18

Mass Number = Number of protons + Neutrons

Number of Neutrons = Mass Number - Number of Protons

Question 19

What is the charge of all atoms?

Answer 19

All atoms are electrically NEUTRAL, meaning NO overall charge
(because number of protons = number of electrons)

Question 20

What is involved in a chemical reaction?

Answer 20

In a chemical reaction, it is the ELECTRONS,
and not the protons or neutrons
that are involved in the reaction.

Question 21

What is the number of electrons in the
outermost valence shell
within each group of the Periodic Table?

Answer 21

Question 22

How are electrons placed?

Answer 22

They are placed in electron shells
surrounding the nucleus (protons and neutrons).

1st shell = max 2 electrons
2nd shell = max 8 electrons
3rd shell = max 8 electrons

Question 23

What is an ion?

Answer 23

An ion is a charged atom or molecule.

It is charged because the
number of electrons do not equal the number of protons
in the atom or molecule.

Question 24

What is a positive ion called?

Answer 24

A Positive Ion is called CATION (read cat-ion).

Question 25

See example of Sodium and Magnesium atoms and cations: How is Sodium ion formed from Sodium atom? How is Magnesium ion formed from Magnesium atom?

Answer 25

Sodium atom (2:8:1) loses 1 electron (1e) to form Sodium ion (2:8) Na - 1e = Na⁺ Magnesium atom (2:8:2) loses 2 electrons (2 e) to form Magnesium ion (2:8) Mg - 2e = Mg²⁺

Question 26

What is a negative ion called?

Answer 26

Negative ion is known as ANION (read as "an-ion").

Question 27

See example of Chlorine and Oxygen atoms and cations: ## Footnote How is Chlorine ion formed from Chlorine atom? How is Oxygen ion formed from Oxygen atom?

Answer 27

Chlorine atom (2:8:7) gains 1 electron (1e) to form chloride ion (2:8:8) Cl + 1e = Cl^- Oxygen atom (2:6) gains 2 electrons (2 e) to form Oxygen ion (2:8) O + 2e = O^2-

Question 28

What are Isotopes?

Answer 28

Isotopes are atoms of the same element. They have the same number of Protons (therefore same element), but different numbers of Neutrons in their nuclei (hence isotopes).

Question 29

What are the similarities and differences between Isotopes?

Answer 29

Similarities: 1. Similar Atomic Number (since proton # same) 2. Similar number of protons; 3. Similar number of electrons (since p # = e #) 4. Similar chemical properties Differences: 1. Different number of neutrons; 2. Hence different mass number (since Mass # = p + n); 3. Different physical properties (eg diffusion rate, density, mass, etc.)

Question 30

Working example of Hydrogen/ Deuterium/ Tritium: Atomic # = Number of p = Mass # = Number of n =

Answer 30

Hydrogen: Atomic # = Number of p = Mass # = Number of n = Deuterium: Atomic # = Number of p = Mass # = Number of n = Tritium: Atomic # = Number of p = Mass # = Number of n =

Question 31

What is a molecule?

Answer 31

A Molecule is a group of 2 or more atoms **chemically** joined together.

Question 32

What is a diatomic molecule? What are common examples?

Answer 32

Diatomic molecules are simple molecules made of 2 atoms chemically joined together. Most non-metallic elements consist of diatomic molecules.

Question 33

What is a carbon dioxide molecule made of?

Answer 33

A chemical combination of carbon and oxygen atoms -- Each molecule would look like this: OCO

Question 34

What is the difference between the molecules of an element v the molecules of a compound?

Answer 34

Molecules of element: consist of fixed number of **1 kind of atoms** Molecules of compounds: consists of a fixed number of **2 or more different kinds of atoms**

Question 35

How can you represent the molecule by a chemical formula?

Answer 35

The formula will show: 1. the number of elements present; 2. the number of atoms of each element present.