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KEY CONCEPT

All living things are based on atoms and theirinteractions.

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Contains:

a. nucleus has protons and neutrons.

b. electrons are in energy levels regions around thenucleus.

Oxygen atom

(O)

Nucleus:8 protons (+)8 neutrons

outermost energy level:6 electrons (-)

inner energy level:2 electrons (-)

An atomsmallest basic unit of matter

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Elements

Matter that has atoms that are all alike are elements. Elements cannot be broken down into smaller

substances.

Elements are listed on the Periodic Table.

More than 90% of the human body is made of onlycarbon, hydrogen, oxygen, and nitrogen.

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Most abundant elements

The most common elements found in living things areCarbon, Hydrogen, Nitrogen, and Oxygen.

Oxygen, at 65%, is the element that makes up mostmass in the human body.

Carbon follows with 18.5%, then hydrogen with 9.5%,and then nitrogen with 3.3%.

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Living things consist of atoms of different elements.

An atom is the smallest basic unit of matter. An element is one type of atom.

H

O

Hydrogen atom (H)

Oxygen atom (O)

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water (H2O)

O

HH

_

++

A compound is made of atoms of different elements

bonded together.

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carbon dioxide (CO2)

Glucose

A compound is made of atoms of different elements

bonded together.

water (H2O)

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An ion forms when an atom gains or loses one or more

electrons. positive ions -formed when atoms lose electrons

negative ions -formed when atoms gain electrons

Ionic bondschemical force due to electircal attractionbetween oppositely charged ions.

Sodium atom (Na) Chlorine atom (CI) Sodium ion (Na+) Chloride ion (CI-)

Na loses anelectron to CI ionic bond

gained electron

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Covalent bonds form when atoms SHARE electrons intheir outer energy level. This allows both atoms tobecome full and stable.

covalent bonds

Oxygen atom (O) Carbon atom (C) Oxygen atom (O)

Carbon dioxide (CO2 )

Molecules- atoms bonded together by covalent bonds

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Covalent bonds

Most organic (coming from living things) compoundshave covalent bonds.

This includes sugars, fats, proteins, and water.

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Compounds you need to know:

H2O = water

CO2 = carbon dioxide

C6H12O6 = sugar (usually glucose)

NaCl = table salt

NH3 = ammonia

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Isotopes

Atoms with the same number of protons and electrons but differentnumbers of neutrons are called isotopes.

Isotopes have the same element, but may have different propertiesbecause of their different masses that may change its stability.

Isotopes are named by adding the number of protons and neutrons.

Some isotopes are useful in telling the age of fossils.