Atoms and Molecules

Do NOT make an ATOM an ION unless it tells you too!

THIS MEANS- Do NOT make an ATOM stable unless it tells you to do so.

To determine the charge of a picture of an atom look at the number of protons and electrons in the picture and determine the charge. (Examples are on the next slide.)

Review:What is the charge of this ATOM? Just use the

number of protons and electrons that are given.

What is the charge of this ATOM? Just use the number of protons and electrons that are given.

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We will discuss:Chemical SymbolAtomsElementsBondsCompoundsMoleculesChemical FormulasEndothermic ReactionsExothermic Reactions

All matter is made of _____________.Atoms

Why would an atom combine with other atoms?

To make the atom stable

When an atom combines with another atom, this forms a ______________________?Molecul

e

When atoms are joined together, they form a _____BOND______.

Atoms bond together for a very simple reason: atoms like to have full valence shells. (8 electrons)

Atoms will share, give away, or gain electrons when forming a bond.

Substances in which 2 or more elements have bonded together form a material with unique chemical properties.

Example: water - 2 Hydrogen atoms bonded to 1 Oxygen atom. H2O

6

C12

Chemical Symbol

Molecules

Are made of ______________ that have been joined together.

ATOMS

Molecules

form when atoms join

ElementCompoun

d

There are two types of molecules

Element MoleculeElement

If a substance has two or more of the same atoms it is a molecule that is an Element

Ex. O (the oxygen we breathe) is made out of two oxygen atoms

Other examples of Element Molecules:H N

O

2

2

3

3

Molecules

Element

H2

If all atoms in a molecule are alike, then the molecule is classified as an

_______________.

ELEMENT

Molecules

form when atoms join

Compound

The other type of molecule is a compound.

Do you think that the atoms joined together in a compound are all the same?

NO! The atoms are different.

Compound MoleculesA combination of two or more different elements

(atoms)Examples:

1 Na atom + 1 Cl atom = the compound NaCl2 H atoms + 1 O atom = the compound H O

The examples above are compounds because the molecule is made out of _____________ atoms.

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DIFFERENT

Energy in Chemical ReactionsOften energy is released or absorbed in

chemical reactions.Where does the energy come from?? Bonds

break or form from electrons being lost or gained.

Energy is released when there is less energy in the products than the reactants. This is called an EXOTHERMIC reaction.

If energy is absorbed there is less energy in the reactants than the products. This is called an ENDOTHERMIC reaction.

Exo = out Endo= in

Chemical Formulas-represent a molecule

O

C

O

The chemical formula of this model is CO

2

COChemical Formula2

CChemical Symbol

The Chemical Formula use symbols and numbers called subscripts to show the elements and number of atoms that make up the molecule.

H O2

Chemical Symbols

SubscriptNote: there are 2 hydrogen atoms and 1 oxygen atom. The one behind the O is imaginary. How many atoms are there? _____

3

H O

Tells Us: There are ______ atoms of hydrogen

and _____ atoms of oxygen.

The name of the elements which are ____________ and ______________.

2

2 1

Hydrogen

Oxygen

CO represents?

Co represents?

Fe O represents?2 3

1 atom of carbon and 1 atom of oxygen

1 atom of cobalt

2 iron atoms and 3 oxygen atoms

Chemical Formulas cont.Writing chemical formulas:

Follow right to left pattern on the Periodic Table of ElementsEx. NaCl sodium is a metal located

on the far left and Cl is located farther to the right

Therefore, the formula is written as NaCl instead of ClNa

If a molecule is made out of one type of atom, it is calledA. Element

If a molecule is made out of different types of atoms it is?

B. Compound

Chemical Equations

•Chemical equation tells about a chemical reaction.

•It shows the substances we start with.

•It shows the new substances that are formed.