Chemistry UnitObjective 4.02

The goal is to be able to evaluate evidence that elements combine in multiple ways to produce various substances

Complete the following• How do you know whether a substance is a compound or a mixture? What

factors need to be present?

Review of Compounds• Compound—two or more substances chemically combine to form a new

substance– Have a definite composition---NaCl is always table salt– Can be broken down into simpler substances by chemical means

meaning NaCl can be broken into Na and Cl– Can be identified by their physical properties meaning how you

observe it and measure it

Molecules• smallest unit of a compound that has all the properties of the compound• Ex smallest molecule of water would be H2O

Chemical Formula• Chemical formula—the

makeup of a compound, uses chemical symbols and subscripts to identify the number of atoms of each element in a molecule of a compound

• Ex. H and O are chemical symbols of hydrogen and oxygen

• 2 the subscript for the number of hydrogen atoms needed to bond with oxygen to make water…this is the formula for water H2O

• When there is not a subscript for a symbol that means there is only 1 atom present, you need one sodium and one chlorine to make salt the chemical formula is NaCl

A CHEMICAL FORMULA IS LIKE A _______ TO A _______

Atom• Atom—smallest unit of an element that has the properties of the element,

also called the building block of an matter

Parts of an Atom• Proton—a particle with a positive charge (+)• Neutron—a particle without a charge (neutral) ( )• Electron—a particle with a negative charge (-)

http://www.chem4kids.com/files/atom_structure.html

Location• Nucleus of Atom contains protons and neutrons• Randomly moving around the nucleus are the electrons

nucleus

More on Electrons• Electrons orbit the nucleus in a region called the electron cloud

• Electrons have different amounts of energy• The closest electrons have less energy than electrons farther from

the nucleus• Electrons on the same energy level have similar amounts of energy

Electrons cont.Energy Level Max Number of Electrons

1 2

2 8

3 18

4 32

How many valence electrons?

• Hydrogen• Fluorine• Neon• Boron• Beryllium• Carbon• Nitrogen • Oxygen• Lithium

Electrons….• Valence electrons are found in the outer shell of the atom

– To determine how atoms combine to make compounds is dependent upon the number and arrangement of valence electrons

• Atomic number=number or protons i.e…27– Number of protons =number of

electrons i.e…27

• Atomic mass(weight) = number of protons + number of neutrons– i.e…58.93

• Symbol=abbreviation of element original name i.e…Co

• Neutrons=atomic mass-atomic number i.e…58-27=31 neutrons

COMPLETE ATOMS FAMILY WORKSHEET

Chemistry UnitObjective 4.02

The goal is to be able to evaluate evidence that elements combine in multiple ways to produce various substances

Complete the following• Write a Haiku about the bond between friends• After you have completed your poem explain how you feel this relates to

atoms bonding

Chemical Bond• Forces that hold atoms together• To bond atoms need to have a total of eight electrons in their outer energy

level • Atoms with 1, 2, or 3 valence electrons normally give their electrons to

atoms of elements that have 7, 6, or 5 valence electrons• Atoms with 4,5,6, or 7 electrons tend to share electrons

Ionic Bonds• when a bond is formed by

losing or gaining electrons– Ion—atom that has gained

or lost one or more electrons

• Losses electrons—atom becomes positive (+)

• Gains electrons—atom becomes negative(-)

• Form because opposite charges attract(+ -)

– Ex NaCl• metal+nonmetal

Covalent Bond• atoms share valence

electrons• Form between

elements whose atoms have 4, 5, 6, or 7 valence electrons

• nonmetal+nonmetal

Elemental Combinations• The same elements and be combined differently to form different

elements – Ex. H2O=water, H2O2=hydrogen peroxide; CO=carbon monoxide, CO2=

carbon dioxide

Lewis Structure• http://library.thinkquest.org/C006669/data/Chem/bonding/lewis.html• This is a website with examples of how to create a Lewis structure

http://www.ausetute.com.au/lewisstr.html

Atomic Theory• All matter is composed of atoms (building block)• Atoms of a given element are identical—same number of protons and

electrons• Atoms of different elements combine in simple whole-number ratios to

form chemical compounds—determined by valence electrons• Compounds can make up living or nonliving substances

• Living—proteins, carbohydrates, fats• Nonliving—plastics, rubber, medicines

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MOLECULAR MODEL LAB