CHAPTER 2CHAPTER 2COMPOSITION OF MATTERCOMPOSITION OF MATTER

MATTER- anything that occupies space and has mass

MASS- quantity of matter an object has

ELEMENT- a pure substance that cannot be broken down into anything simpler kinds of matter (over 100 but fewer than 30 are important to living things)

ATOMATOM

The smallest unit of an element.

The properties of an ATOM are determined by the number and arrangement of Protons, Neutrons, and Electrons

ATOMATOM

PROTONS- large particle with a POSITIVE charge found in the nucleus

NEUTRONS- large particle with NO charge found in the nucleus

ELECTRONS- small particle with a NEGATIVE charge- LOCATED IN ENERGY LEVELS

ATOMSATOMS

• ATOMS- have the same number of electrons and protons therefore they have no overall charge. ATOMS ARE ALWAYS NEUTRAL (although some are not stable in nature)

• ION- an atom that has lost or gained electrons and therefore has a charge - either negative ( gained ) or positive ( lost)

ATOMIC NUMBER of an elementATOMIC NUMBER of an element

Is equal to the number of PROTONS found in the nucleus

ATOMIC MASSATOMIC MASS

The total number of PROTONS and NEUTRONS in the nucleus.

WHERE ARE ELECTRONS? WHERE ARE ELECTRONS?

• ELECTRONS EXACT LOCATION CAN NOT BE DETERMINED

• The best scientists can do is calculate the chance an electron in a given location due to the shading of the electron clouds.

• Since these clouds seem to be in rings at varying distances they are called ENERGY LEVELS or ORBITALS

ELECTRONSELECTRONS

• ORBITALS- regions in an atom where electrons are likely to be found.

• As the orbitals move further away from the nucleus the electrons must have more energy to occupy that space.

• Electrons will occupy the orbitals that require the lowest amount of energy first.

• 1st energy level lowest energy level and can hold ONLY 2 ELECTRONS-

• 2nd energy level- can hold 8 electrons• 3rd energy level- will be stable with 8 electrons.

How electrons fill up orbitalsHow electrons fill up orbitals

VALENCE ELECTRONVALENCE ELECTRON

• VALENCE ELECTRONS- electron that is found in the outermost energy shell, (has the most energy) and determines the atom’s chemical properties.

COMPOUNDCOMPOUND

Defined as atoms of 2 or more elements that Defined as atoms of 2 or more elements that combine together chemically to form a new combine together chemically to form a new substance with different chemical substance with different chemical propertiesproperties

Example hydrogen gas + oxygen gas = Example hydrogen gas + oxygen gas = WATER WATER

Give me 3 examples of compounds.- Give me 3 examples of compounds.- BrainstormBrainstorm

MOLECULEMOLECULE

2 or more atoms forming a chemical 2 or more atoms forming a chemical bond, smallest unit of a compound that bond, smallest unit of a compound that retains the properties of that retains the properties of that compoundcompound

Example : HExample : H22 O O

Two hydrogen atoms chemically bonded Two hydrogen atoms chemically bonded to one oxygen atomto one oxygen atom

Why are Compounds Why are Compounds Made?Made?

Compounds are formed to make the Compounds are formed to make the atoms more stable.atoms more stable.

An atom is chemically stable WHEN An atom is chemically stable WHEN ITS OUTERMOST ENERGY LEVEL ITS OUTERMOST ENERGY LEVEL IS FULL OF ELECTRONSIS FULL OF ELECTRONS

UNDERSTANDING THE UNDERSTANDING THE PERIODIC TABLEPERIODIC TABLE

What is a METAL? Where are they What is a METAL? Where are they located on the periodic table?located on the periodic table?

What is a NONMETAL? Where are What is a NONMETAL? Where are they located on the periodic table?they located on the periodic table?

What is a NOBLE gas? Where are What is a NOBLE gas? Where are they located on the periodic table? they located on the periodic table? Why are they called NOBLE?Why are they called NOBLE?

3 types of bonds3 types of bonds

1.1. METALLIC BOND-METALLIC BOND- bond between bond between two metals-two metals-

2.2. COVALENT BOND-COVALENT BOND- bond between bond between two non metalstwo non metals

3.3. IONIC BONDIONIC BOND – bond between a – bond between a METAL and NONMETALMETAL and NONMETAL

IONIC BONDIONIC BOND

IONIC BOND- the attraction of positive and IONIC BOND- the attraction of positive and negative electrical charges of the ions to negative electrical charges of the ions to each other. each other.

Step 1- Valence electrons are lost or gained Step 1- Valence electrons are lost or gained and the atom becomes an ionand the atom becomes an ion

Step 2- Ionic charges are attracted to each Step 2- Ionic charges are attracted to each otherother

Ionic bonds are easily broken in water and Ionic bonds are easily broken in water and allow the water to conduct electricity allow the water to conduct electricity

How can items with the How can items with the same charge make a same charge make a

molecule?molecule?ANSWER- The SHARE the valence ANSWER- The SHARE the valence

electronselectrons

Example OExample O22 and CO and CO22

COVALENT BONDSCOVALENT BONDS

Two or more atoms share one or more Two or more atoms share one or more pairs of electrons. pairs of electrons.

Covalent bonds are much stronger than Covalent bonds are much stronger than ionic bonds. ionic bonds.

IN your notes DRAW THE COVALENT IN your notes DRAW THE COVALENT BONDS of 2 hydrogen atoms and 1 BONDS of 2 hydrogen atoms and 1 oxygen atom to make a water oxygen atom to make a water molecule.molecule.

COVALENT BONDSCOVALENT BONDS In science we typically draw the covalent bonds In science we typically draw the covalent bonds

by drawing a line between the two elementsby drawing a line between the two elements

One line- means the sharing of 2 electrons (1 One line- means the sharing of 2 electrons (1 pair)pair)

Two lines- means the sharing of 4 electrons (2 Two lines- means the sharing of 4 electrons (2 pair)pair)

Three lines- means the sharing of 6 electrons (3 Three lines- means the sharing of 6 electrons (3 pair)pair)

Draw the symbol of a water molecule showing Draw the symbol of a water molecule showing the covalent bondsthe covalent bonds

COVALENT BONDSCOVALENT BONDSELEMENT ELEMENT NUMBER OF NUMBER OF

COVALENT COVALENT BONDSBONDS

EXAMPLESEXAMPLES

HydrogenHydrogen

ChlorineChlorine

FluorineFluorine

OxygenOxygen

SulfurSulfur

NitrogenNitrogen

CarbonCarbon