Atomic Structure

BASIC INFORMATION

• atoms are made up of: protons (+ charge)neutrons (no charge)electrons (- charge)

• atomic number = # protonsLithium’s atomic # is 3

• atomic mass = # protons + # neutronsLithium’s atomic mass is 6.94 (round to 7)

• in a neutral atom: # protons = # electrons

Lithium has 3 electrons• the # neutrons = atomic mass - # protons

Lithium has 4 neutrons (7 – 3 = 4)

About Atoms…..

ELECTRONS ARE ELECTRONS ARE ARRANGED IN ARRANGED IN

“SHELLS” AROUND “SHELLS” AROUND THE NUCLEUSTHE NUCLEUS

Element: Boron Mass =

Symbol: B # P =

# Neutrons = # e =

# Valence Electrons =

The first electron shell can hold up to 2

electrons

The second electron shell can hold up to 8

electrons

The third electron shell can hold up to 8

electrons

In biology, we usually don’t have to deal

with elements having more than three electron shells!

Which of an atom’s electrons are involved in bonding with

other atoms? Only the electrons in its Only the electrons in its outermostoutermost shell! shell!

These electrons are called the These electrons are called the valence valence electronselectrons!!

Hydrogen atoms Hydrogen atoms have have

1 valence electron1 valence electron

Helium atoms Helium atoms havehave

2 valence 2 valence electronselectrons

Element: Boron Mass # =

Symbol: B # P =

# Neutrons = # e =

# Valence Electrons =

First shell 2 electrons

Second shell 8 electrons

Third shell 8 electrons

Fourth shell 16 electrons

Now, Now, complete your complete your worksheets !worksheets !

• atoms are made up of: protons (+ charge)neutrons (no charge)electrons (- charge)

• atomic number = # protonsLithium’s atomic # is _____

• atomic mass = # protons + # neutronsLithium’s atomic mass is _____

•in a neutral atom: # protons = # electrons

Lithium has _____ electrons• the # neutrons = atomic mass - # protons

Lithium has _____ neutrons

About Atoms…..

ELECTRONS ARE ELECTRONS ARE ARRANGED IN ARRANGED IN

“SHELLS” AROUND “SHELLS” AROUND THE NUCLEUSTHE NUCLEUS

Element: Boron Mass =

Symbol: B # P =

# Neutrons = # e =

# Valence Electrons =

The first electron shell can hold up to

_____ electrons

The second electron shell can hold up to

_____ electrons

The third electron shell can hold up to

_____ electrons

In biology, we usually don’t have to deal

with elements having more than three electron shells!

Which of an atom’s electrons are involved in bonding with

other atoms? Only the electrons in its Only the electrons in its ________________________ shell! shell!

These electrons are called the These electrons are called the ________________________________!!

Element: Boron Mass # =

Symbol: # P =

# Neutrons = # e =

# Valence Electrons =