Introduction to the Periodic Table

Atom Review

Atom Review

▪ The atom consists of a nucleus surrounded by orbitals.

Atom Review

▪ The nucleus contains positively charged protons and neutral (no charge) neutrons.

Atom Review

▪ Negatively charged electrons circle the nucleus in the orbitals.

▪ There are 2 electrons in first orbital.

Electron Orbitals

Time Line

1750. Only 17 elements had been identified.

1789.Antoine Lavoisier grouped the known elements into metals, nonmetals, gases, and earths. The unknown elements caused problems.

Time Line

1860s Dmitri Mendeleev organized the 63 known elements into a periodic table based on increasing mass with elements with similar properties in the same columns. He left spaces for the unknown elements.

Mendeleev’s Periodic Table

Time Line

1875. Gallium fit into the table as expected based on its melting point and density.

1879. Scandium fit as expected.

1886 Germanium fit as expected.

Protons

▪ Protons where discovered in 1918 by Ernest Rutherford.

▪ Mendeleev had no knowledge of them.

Protons

▪ All atoms of an element have the same number of protons.

▪ They do not all have the same atomic mass.

Periodic Table

▪ Because of this, the modern table is arranged in order of increasing atomic number or number of protons.

Periodic Table

Isotopes

▪ The atoms of the same element with different masses are isotopes.

▪ They have different numbers of neutrons.▪ The atomic mass given on the table is an

average of all known masses for the element.

Periodic Table

▪ Rows are called periods.▪ There are seven of these.▪ The number of orbitals increases from one

period to the next.

Periodic Table

▪ Columns are called groups.▪ Groups have similar properties because they

have similar electron configurations.▪ The electron configurations determine their

chemical properties.▪ That pattern is called the periodic law.

Periodic Table

17

ClChlorine

35.453

Aatomic # #

Element symbol

Element name

Atomic mass

Math

▪ Atomic mass = protons + neutrons▪ Atomic number = protons▪ Protons = electrons (atoms are neutral/no

charge as listed on the periodic table)

AMU

▪ Atomic mass unit▪ Because the mass of an atom in grams is very,

very small we measure the mass of individual atoms in amu.

▪ Each proton and neutron counts a 1 amu.▪ For example: carbon has 6 protons and 6

neutrons so its mass is 12 amu

Elements(WRITE THE UNDERLINED NOTES!!!!)

Periodic Table

▪ Elements 1-92 except 43 and 61 occur naturally on Earth.

▪ (The others can be made through process we will talk about in the future.)

Elements

▪ Elements are grouped into 3 groups:▪ Metals▪ Nonmetals▪ Metalloids

Metals

▪ Most of the elements are metals.▪ They are on the left side and middle of the

periodic table.

Properties of Metals

▪ Except for mercury, they are all solid at room temperature.

▪ They are good conductors of electric current and heat.

Properties of Metals

Properties of Metals

▪ They are malleable (bendable).

Properties of Metals

▪ They are ductile (can be drawn into thin wires).

Properties of Metals

▪ They range from extremely reactive to difficult to make react.

Transition Metals

▪ Groups 3-12

Transition Metals

▪ They were among the 1st elements discovered.▪ They are able to form compounds with distinct

colors.▪ These groups have more in common than other

groups on the table.

Transition Metals

Nonmetals

▪ Located on the right side of the table except for hydrogen.

Nonmetal Properties

▪ Poor conductors of heat and electricity

Nonmetal Properties

▪ Low boiling point▪ All gases are nonmetals but not all nonmetals

are gases.

Nonmetal Properties

▪ Brittle if solid at room temperature

Nonmetal Properties

▪ Reactivity varies▪ Fluorine is the most reactive nonmetal.▪ Group 18 are the least reactive elements on the

table.

Metalloids

▪ Separate metals and nonmetals on the table.▪ Conductivity varies▪ Changes in temperature cause some to change

from good insulators to good conductors.

Trends

▪ As you move from left to right across the table, elements become less metallic and more nonmetallic in their properties.