Atoms, Elements

Atoms

Protons Neutrons

Electrons

Contain 3 particles

Nucleus

Consists of:NeutronsProtons

The Neutron

What are the characteristics of the particles?

• No Charge

• Determines isotope

The Proton

• Positive charge

• Determines element

The Electron

• Negative charge

• Participates in chemical reactions

• Outer shell e- determine chemical behavior

Atoms

• The number of electronsThe number of electrons

Is equal to the number of protonsIs equal to the number of protons

• Electrons in space around the nucleusElectrons in space around the nucleus

What is the atomic number?Number of protons

Number of protons plus neutrons

13Al

26.9815

Atomic number

Symbol

Mass number

What is the mass number?

Atomic Number?

C atom with C atom with

CarbonMass Number?

____

____

• ____ protons____ protons

• ____ neutrons____ neutrons

6

12

6

6

Helium Atomic Number? ____

Mass Number? ____

He

Protons? ____Neutrons? ____2

2

2

4

4

2

Biologically Important Elements

Oxygen (O)

Carbon (C) Hydrogen (H)

Nitrogen (N)

Trace elements

Calcium (Ca)Phosphorus (P)Potassium (K)Sulfur (S)Sodium (Na)Chlorine (Cl)Magnesium (Mg)

Bonds are formed or broken down in chemical reactions

• Ionic bonding– Atoms losing or gaining electrons to

complete their outer shells

• Covalent bonding

– Sharing electrons

• Covalent bonding

– Sharing electrons

Covalent bonds can be:

Single

Double

Triple

WaterOur cells are composed of 70% –95% water

Water covers 3/4th of the earth

The electrons in its covalent bonds are shared unequally

How are the hydrogen and oxygen atoms bonded together?

Hydrogen bonding?Covalent bonding?

Creates POLARITY

Water

WaterHydrogen bonding?Covalent bonding?

How are water molecules bonded together?

The polarity of water results in weak electrical attractions between neighboring water molecules

Creates HYDROGEN bonding

An acid

What is:

– A compound that accepts H+ ions and removes them from solution? A

base

A pH scale

– A chemical compound that donates H+ ions to solutions?

– A measure of H+ ion concentration in a solution?

A pH Scale

Acidic

Basic

Neutral pH 7

– Biological range maintained at ~ 6.5 – 7.5

• Blood ~ 7.2 – 7.4

[H+] = [OH+]