Atoms, Elements, and Molecules

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Matter

Matter is anything that has mass and takes up space

Most of what we see is matter

Matter is made of atoms

What are atoms?

Atoms

Atoms are the smallest building blocks of matter that can chemically change This means that they are the smallest

piece of matter that has chemical properties

Since atoms make up matter, and matter makes up almost everything we know, it means almost everything is made of atoms

Atoms are made of different parts

Parts of the Atom

The atom is made of basic 3 parts:

Protons

Neutrons

Electrons

Both found in the nucleus

‘Orbits’ outside the nucleus

Parts of the Atom - Nucleus The center of the atom is called the nucleus

It holds all of the mass of the atom

There are 2 parts of the nucleus:

Protons – positively charged

Neutrons – not charged

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Parts of the Atom - Electrons Electrons ‘orbit’ outside of the

nucleus

Electrons are negatively charged

Electrons weigh about 2000 times less than protons or neutrons, so we assume the nucleus has all of the mass

Electrons orbit REALLY far away from the nucleus 6

Electrons

Electrons are really far away from the nucleus

If the nucleus were the size of a marble and that marble was placed on the middle of a soccer field, the electrons would far outside the outside of the stadium.

This means that atoms are almost entirely empty space

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Atoms and Elements There are different types of atoms

Each type of atom is called an element

There are 92 naturally occurring elements and 26 man-made elements

Each element has it’s own unique physical and chemical properties

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Elements Elements are listed on the Periodic Table of

Elements

Each elements has its own square on the Periodic Table

Each element has a 1 or 2 letter symbol called a chemical symbol The first letter is ALWAYS a capital letter The second letter (if present) is ALWAYS

lower case. 9

Chemical Symbol Examples

What are the symbols for the following elements?1. Hydrogen

2. Boron

3. Oxygen

4. Magnesium

5. Einsteinium

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What elements have the following symbols?1. C

2. Ne

3. Kr

4. Mn

5. Au

6. U

Elements and Protons The number of protons

tells us the type of element the atom is The number of

protons gives an atom its identity

Protons are abbreviated p+

The number of protons in the nucleus of atom is the Atomic Number

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OOxygen

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16.00

Atomic Number = Number of Protons

The atomic number MUST be a positive integer

Element Examples

How many protons do the following elements have?

1. Oxygen

2. Fluorine

3. Titanium

4. Sodium

5. Silver

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Which elements have the following atomic numbers?

1. 24

2. 58

3. 11

4. 100

5. 3

Elements and Neutrons Neutrons are uncharged particles in the

nucleus Neutrons are abbreviated n0

When you add the number of protons with the number of neutrons, you get the Atomic Mass

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OOxygen

8

16Atomic Mass

Atomic Mass

(# of p+) + (# of n0) = Atomic Mass Eg. Oxygen (# of p+) + (# of n0) = Atomic Mass (8) + (# of n0) = 16 (# of n0) = 8 Oxygen-16 has 8 neutrons in its nucleus

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OOxygen

8

16 Atomic Mass

Atomic Number = Number of Protons

Atomic Mass Examples

What is the atomic mass of the following atoms?1. Nitrogen with 8 n0

2. Calcium with 20 n0

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Elements always have the same number of protons but can have different numbers of neutrons in their nucleus

The same element, with different numbers of neutrons are called Isotopes

Eg. All carbon atoms have 6 protons, but they can have 6, 7, or 8 neutrons. Carbon-12, Carbon-13, and Carbon-14 are all isotopes of carbon 16

Neutrons

Atomic Mass Example

Eg. How many neutrons are in the following isotopes of Calcium?

Calcium-40

Calcium-42

Calcium-48

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Atomic Mass as an Integer

Since the atomic mass is the sum of 2 integers (number of protons and number of neutrons), the atomic mass is ALWAYS an integer

It is an irrational number on your periodic table it is because that is an average of the masses of isotopes

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Electrons Electrons determine the behaviour of an

element They give an element its physical and

chemical properties

The number of electrons is usually the same as the number of protons

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Electron Examples

How many electrons would the following atoms have?1. Nitrogen

2. Helium

3. Potassium

4. Molybdenum

5. Bohrium

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What elements have the number of electrons?1. 6

2. 11

3. 42

4. 56

5. 96

Electrons

Remember when I said that atoms have the same number of electrons and protons…

That’s not always the case

Electrons

Atoms can change their number of electrons frequently

This is because electrons are held loosely by the nucleus

This is also really important because if they couldn’t, we wouldn’t be alive!

Electrons

Atoms are called neutral if they have the same number of protons and electrons

This is because if an atom have the same number of protons and electrons, the atom has no charge

Eg. – Hydrogen Has 1 proton and 1 electron

(+1) + (-1) = 0

No charge is neutral

Ions

Atoms that lose or gain electrons are called ions

Ions have a charge

When writing the charge, it always goes in the top right-hand corner. Eg. Fluorine with a -1 charge gets is shown as:

F-

Eg. Selenium with a charge of -2 is shown as:

Se2-

Cations

If an atom loses electrons, it gets a positive charge

Atoms with a positive charge are called cations

Cation Examples

1) How many electrons would each of the following have? Beryllium loses 2 electrons Sodium loses 1 electron

2) What is the charge on each of the following atoms? Aluminum loses 3 electrons Silicon loses 4 electrons

Anions

If an atoms gains electrons, it gets a negative charge

Atoms with a negative charge are called anions Think of it like this, A-Negative-ion, A-N-ion

Anion Examples

1) How many electrons would each of the following have?– Fluorine gains 1 electron– Phosphorus gains 3 electrons

2) What is the charge on each of the following atoms?– Sulphur gains 2 electrons– Chlorine gains 2 electrons

Can we go smaller?

If matter is made of atoms; and atoms are made of protons, neutrons, and electrons; what are protons, neutrons, and electrons made of?

How small can we go?

Compounds So far we learned about elements, 1 type of pure

substance

The other type of pure substance is a compound

Compounds are 2 or more elements hooked (sometimes called bonded) together

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Compounds Compounds are made of 2 or more

combined elements

However, they have completely different chemical and physical properties than the elements they are made of

Example – Sodium is a silver metal that explodes when it touches water. Chlorine is a poisonous gas that destroys lung tissue. Sodium Chloride is salt and is necessary for life

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Chemical Formulas

Molecules are another name for compounds

All compounds are represented with a special notation Write the chemical symbol of each element in

the compound If there is only 1 atom of that element in the

compound, leave it alone If there are 2 or more atoms of an element,

write a small number in the bottom right hand of the chemical symbol 32

Writing Chemical Formulas Example – Write the chemical formula for Calcium

Carbonate. It is 1 calcium, 1 carbon, and 3 oxygens.

Write the chemical symbol of each element Ca C O

Write the number of the atoms in the bottom right corner of the chemical symbol

CaCO3

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Chemical Formula Examples Write the chemical

formula for each compound1. Hydroiodic acid – 1

hydrogen, 1 iodine

2. Hydrogen Peroxide – 2 hydrogen, 2 oxygens

3. Glucose – 6 carbon, 12 hydrogen, 6 oxygen

4. Sulphuric Acid – 2 hydrogen, 1 sulphur, 4 oxygen

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Determine which elements, and how many of each, are in the following compounds1. BaCl2

2. N2

3. Fe2O3

4. KCo2F5

5. U3O8