Atomic Structure

Atom• Basic unit of matter• Made of subatomic particles

Element• Substance made of same type of atom

Protons• Positive Charge• Located in the nucleus• Mass = 1 amu– Helps make up the mass of an atom

• # of protons never changes for an element– Same as atomic number

Neutrons• No Charge• Located in the

nucleus• Mass = 1 amu– Helps make up the

mass of an atom– Can differ in atoms of

the same elementHow to Calculate

NeutronsMass # - Atomic # = Neutrons

Electrons• Negative Charge• Located in the electron cloud– Surrounds the nucleus– Move very fast!

• Mass = 0 amu– Does not really count towards an atom’s mass

• In neutral atoms, electrons = protons

Atomic Number• Special for every element

• Tells # of protons (and electrons)• Located on the periodic table (whole number)

Atomic Mass• Located on periodic table– Has decimals

• Average mass of the element’s isotopes

Mass Number• Protons + Neutrons• Whole Number (rounded atomic mass)

Practice•How many protons does nitrogen have?

Practice•What is the atomic mass of calcium?

Practice•What is the mass number of calcium?

Practice•How many neutrons are in chlorine?

Practice•Name of Element:

•Atomic Number:

•Atomic Mass:

•Mass Number:

•Protons:

•Neutrons:

•Electrons:

Practice•Name of Element:

•Atomic Number:

•Atomic Mass:

•Mass Number:

•Protons:

•Neutrons:

•Electrons:

Practice•Name of Element:

•Atomic Number:

•Atomic Mass:

•Mass Number:

•Protons:

•Neutrons:

•Electrons:

Just How Small Are Atoms?

Isotopes• Same element with different numbers of

neutrons; therefore, different masses• EX: Carbon-12 Carbon-14

6 12 C 6 14 C

Practice• How many neutrons in

Potassium-39Potassium-41Fluorine-19Fluorine-18

Practice• Ni-60–Protons?–Electrons?–Mass number?–Neutrons?

Practice• Magnesium-26–Protons?–Electrons?–Mass number?–Neutrons?

Practice• 15 29 P–Protons?–Electrons?–Mass number?–Neutrons?

Ions• Charged atom• Gain or lose 1 or more electrons• Proton number does not change

PracticeHow many electrons in a neutral

atom of Na?

How many protons in Na?

How many electrons in Na +1

PracticeHow many electrons in a neutral

atom of S?

How many protons in S?

How many electrons in S -2?