Periodic Table

Periodic Table• The periodic table is a chart containing information

about the atoms that make up all matter.• It is called the periodic table of elements because

elements are made of the same kind of atom.

Periodic Table• In the periodic table we can learn element’s

names, their atomic number, number of protons, neutrons, and electrons, number of valence electrons and atomic mass.

Element

• An element is a substance made up of only one type of atom.

ATOMIC NUMBER ELEMENT SYMBOL

ELEMENT NAME

ATOMIC MASS

Atomic Number• The atomic number of an atom is equal to the

number of protons in its nucleus.• How many protons to the following elements have?a) magnesium

b) lead

c) aluminum

Number of Electrons• All neutral atoms have the same number electrons as protons. The

atomic number tells us the number of protons, and it also tells us the total number of electrons.

• The number of electrons surrounding the nucleus of an atom is equal to the number of protons in its nucleus.

• How many electrons do the following elements have?a) potassium

b) sulfur

Atomic Mass

• The atomic mass tells us how much an atom weighs.• Atomic mass is equal to the number of protons plus the

number of neutrons.• Atomic mass is measured in “atomic mass units” (amu)

Demo

Atomic Mass

- Xenon - atomic mass of

131.293 amu- Protons + Neutrons

= 131.293 amu

Atomic Mass

•Xenon has an atomic mass of 131.293 amu

•To find the number of neutrons1) We round the atomic mass: 131 amu2) We subtract the atomic number from the atomic mass:

131 – 54 = 77

-(atomic mass - # protons = # neutrons)-(Big # – small # = # of neutrons)

Atomic Mass• Using your Periodic Table of Elements find the

atomic mass of the following:1) Nitrogen

2) Barium

3) Mercury

4) Argon

Number of Neutrons• To find the number of neutrons:1) We round the atomic mass: 2) We subtract the atomic number from the atomic mass:

(atomic mass - # protons = # neutrons)• How many neutrons do the following atoms have? Show

your work!a) beryllium b) sodium

Finding Number of Neutrons Example

•Xenon has an atomic mass of 131.293 amu

•To find the number of neutrons1) We round the atomic mass: 131 amu.2) We subtract the atomic number from the atomic mass:

131 – 54 = 77-(atomic mass – # protons = # neutrons)-(Big # – small # = # of neutrons)

Periods• Periods are the horizontal rows in a periodic table.• Periods tell us about how electrons sit around the

nucleus, depending upon the element.• Write the period number beside each row.

Groups/Families• Groups or families are the vertical columns in a periodic

table.• All the elements in the same group have the same number

of valence electrons.• All the elements in the same group have similar chemical

characteristics.• Write the group number

that has the letter A besideit for each group.

Valence Electrons• Electrons have different orbits around the nucleus.• Valence electrons are the electrons that are on the

outermost orbit.• We can tell how many valence electrons an element has

based on which group it is in. Look at the groups with the letter ‘A’ in them!

Valence Electrons

• How many valence electrons do the following elements have?

1) Boron2) Chlorine3) Calcium4) Cesium5) Oxygen