Brain pop- atom

Atomic number a. equals the number of protons in the nucleus (AN = p+) b. It is specific to each element c. It is a whole number written above the element’s symbol d. The proton # does not change due to a physical change in

state or a chemical reaction. e. In an atom the number of electrons equals number of

protons, because atoms are neutral (no charge).

Mass Number a. equals the total number of protons and neutrons in the

nucleus. b. MN= p+ + nº (rounded whole number of atomic mass). c. Atomic Mass written under the elements symbol d. Electrons mass is too small to make a difference in the

total mass of the element. e. The number of neutrons equals the mass number minus

the atomic number. (nº) = MN – AN (p+)

Mass number

Example & practice

Gold (Au) Atomic Number = protons (never changes) =_______ Electrons =______(atom is neutral) Mass Number = _______ Neutrons = MN – AN = _________________

Practice (15 min) Then periodic table notes

The Periodic Table & Element

Classes

The first version of the periodic table was created by Dmitri Mendeleev a Russian chemist and inventor.

He organized it by atomic mass (P+N) going down and he realized elements had similar properties going across.

Henry Moseley(1887-1915) –used his research to arranged the elements by increasing atomic number (#of Protons) going across.

In this new arrangement the elements have similar properties going down each column or group.

Group or Family Period

Metals

Metals- 80% of all elements

PROPERTIES:

Shiny—metallic luster

Malleable—can be hammered or rolled into sheets

Ductile—can be stretched into fine wires

Tensile strength— resists breaking

Most are solid at room temperature (except mercury)

Good conductors of electricity and heat

Alkali Metals

Alkali Metals • NEVER found pure in nature

because they are too reactive

• Reactivity of these elements increases down the group

• Group 1= Have 1 valence electron

Potassium, K reacts with water and must be stored in kerosene

Alkaline Earth Metals

Alkaline Earth Metals • less reactive than alkali metals • not found pure in nature; they are too reactive • The word “alkaline” means “basic”

– common bases include salts of the metals • Ca(OH)2

• Mg(OH)2

• Group 2 = 2 valence electrons

Transition Metals

Transition Metals

(still a metal just transitioning to non-metal)

Copper, Cu, is a relatively soft metal, and a very good electrical conductor.

Mercury, Hg, is the only metal that exists as a liquid at room temperature

Metaloides

Properties of Metalloids

• have properties of both metals and nonmetals.

• Border the stairs

• more brittle than metals, less brittle than most nonmetallic solids

• semiconductors of electricity • Some metalloids possess

metallic luster

Silicon, Si & Germanium, Ge

Si and Ge are great semiconductors of electricity at high temperatures.

used in the circuitry of computers, digital watches, televisions, and radios.

Nonmetals

Nonmetals- 20% of elements

• Brittle

• Gases at room temperature (except: bromine= liquid, iodine, sulfur, selenium, phosphorus &carbon are all solid)

• Poor conductors of electricity and heat

• HYDROGEN is a nonmetal

Carbon, the graphite in “pencil lead” is a great example of a nonmetallic element.

Halogens • never found pure in nature; they

are too reactive

• in their pure form are diatomic molecules (F2, Cl2, Br2, and I2)

• Group 7= 7 valence electrons

Chlorine is a yellow-green poisonous gas

Noble Gases

Noble Gases • They are ONLY found pure in nature –

they are chemically unreactive!!

• Colorless, odorless and unreactive; they were among the last of the natural elements to be discovered

• Group 8 = 8 valence electrons (except helium, which has only 2)

Periodic table activity 30 minutes if not done finish for HW