Unit 1 Chemistry of Life: Atoms and Molecules

Elements Required for LifeApprox 25 elementsC, O, H and N 96% of living matterP, S, Ca and K 4% of an organism’s weightTrace elements

Needed in minute quantities Ex. Fe, I, Mg

MatterAnything that takes up space and has massSolid, liquid, gasElements cannot be broken down further

Fe, Rb, FrCompounds consist of two or more elements

NaCl, H2O, H2CO3

Periodic Table of Elements

GroupsPeriodsAtomic

numberAtomic

massMetals/

NonmetalsFamiliesTrends

Chemical FamiliesAlkali metalsAlkaline earth metalsMetalloidsHalogensNoble gasesTransition metalsActinide/Lanthanide Series

Atomic Structure

Atom-Smallest unit of matter Subatomic particles-Parts of atom

Neutron/proton

mass=1.7X10-24 g (1

Da or amu)

Mass of electron is negligible (1/2000)

Atomic Number and Weight

All atoms of an element have same number of protons; this is atomic number

2HeAll atoms have a balanced charge, therefore:

Atomic number=Protons=ElectronsMass number=Protons + neutrons (round

mass #)Mass number – atomic number

(protons)=NeutronsAll of atom’s mass is in nucleus; this is atomic

weight

Isotopes

Atoms of a given element that contain different number of neutrons, but same protons

All natural elements exist as a mixture of all its isotopes

Some are radioactive isotopes which have a spontaneously decaying nucleus Radiology

Energy Levels

Each electron shell contains a certain amount of energy (n)

As you move up the energy increases

e- moving up absorbs energye- moving down loses energy,

releasing heat# e- in each level=2(n)2

For atomic structure: Place neutrons and protons in

nucleus Arrange e- using 2n2

Valency

The number of electrons that orbit the outermost energy level

This is equivalent to the charge

Chemical Bonding

All bonding occurs in the outer shell of atoms (sharing of valance e-)

Types of bonds: Covalent Bonds-Sharing of a pair of valence electrons by two

atoms. Non polar covalent: e- are shared equally (methane) Polar covalent: Unequal sharing of e-. One tends to pull harder

(HCl or water) Ionic Bonds-Transfer of e- from the negative ion to the positive

ion. Ion-Element that loses or gains an electron

Hydrogen Bonds-Hydrogen atoms bonded to electronegative atoms

Van Der Waals Interactions-All atoms and molecules when close to each other tend to “stick” to one another. Occurs due to natural gravitational forces of atoms

Non-Polar