Atoms and Elements

Notes

Matter

• Anything that has mass and takes up space

• Made of atoms

Matter

Matter

Anything that has mass and takes up space

Atom

Smallest unit of matter

Proton:

Positive & in the nucleus

Neutron: neutral & in the nucleus

Electron:

Negative, tiny, & outside of the nucleus

ATOMS

• Smallest unit of matter.– Atoms make up everything (that has mass

and takes up space).

Protons (+)

• Determines the identity of the Element

• Represents the Atomic #

• Positively charged• Nucleus• Part of the atoms

mass

Neutrons – No charge

• Neutral – No charge

• Nucleus

• Part of the atoms mass

Electrons (-)

• Negatively charged• smallest particles• Outside nucleus• Found in the

electron cloud • Located in energy

levels

Atomic Particle Size

Nucleus

• Center of the atom• Made up of Protons and Neutrons• Makes up the atoms MASS• Positively Charged!

Electron Cloud

• Area around the nucleus where electrons are found.

• Negatively Charged

Energy Levels

• Levels within the electron cloud that hold a specific # of electrons.

– 1st level - 2 electrons– 2nd level - up to 8 electrons– 3rd level – up to 8 or 18

Valence Electrons

• Electrons on the outermost energy level of the atom.

• Determine the atoms chemical properties, including reactivity.

Atomic Structure Review

• Protons (+) – make up the

nucleus

• Neutrons (no charge)

– Make up the nucleus

• Electrons (–) – Found in energy

levels around the nucleus in the electron cloud

Atomic Number

• Top # on the periodic table• # of protons in the atom

– Atomic # = 2– 2 protons

Chemical Symbol

• 1 or 2 letter abbreviation for an element name– 1st letter Capitalized– 2nd letter – always lowercase

• Helium - He

Atomic Mass

• Bottom #• Mass of the atom• Located in the nucleus• Equal to Protons + Neutrons

Determining the # of subatomic particles in

atoms Use the following

A = P = E M – A = N

Atomic # = Protons = Electrons

Mass – Atomic # = Neutrons

Atom Models

Valence Electrons

• The electrons in the outermost energy level of the atom.

• What element is this?

• How many valence electrons does it have?

ELEMENTS

• All the atoms that make up our universe• Identified by the atomic # (# of protons)

3 Main Groups on the Periodic Table

Metals

• Make up most of the elements• All solid except Mercury• Has luster (shiny)• Good conductors of heat and

electricity• Malleable – hammered or shaped

into thin sheets• Ductile – stretched into wires

Metals

Nonmetals

• Usually gases or brittle solids• Poor conductors of heat and

electricity– They are insulators

• Right side of the periodic table• Only 17 nonmetals

Metalloids

• Called Semi-metals• Share properties of both metals and

nonmetals• Located on the zig-zag

line between the metals and nonmetals.

Groups/Families

• 18 groups • Vertical Columns on

the periodic table • Same # of valence

electrons• Same chemical

properties including reactivity

• Reactivity – Elements tendency to undergo chemical reactions

Periods

• 7 horizontal rows on the periodic table

• Consist of elements with the same number of electron levels.

Alkali Metals

• Group #1• All metals• 1 Valence Electron• Very reactive• Most reactive – the

only need to lose 1 valence electron in chemical bonds

Alkaline-Earth Metals

• Group #2• All Metals• 2 Valence

Electrons• Very reactive but

less than group #1.• Only have to lose 2

valence electrons in chemical bonds

Valence Electrons

• Group 1 – all elements have 1 valence electron

• Group 2 – all elements have 2 valence electrons

Transition Metals

• Groups # 3-12

• All metals

• 1 or 2 valence electrons

• Less reactive than group #2

• Also contains lanthanide and actinide series

Groups # 13-16

• Elements change from metals to nonmetals and include the metalloids.

• Atoms have 10 fewer valence electrons than the group #.

• Boron Group #13 - 3 valence electrons• Carbon Group #14 - 4 valence electrons• Nitrogen Group #15 - 5 valence electrons• Oxygen Group #16 - 6 valence electrons

Halogens

• Group 17• All nonmetals• 7 valence electrons• Very reactive

– Only need to gain 1 more electron for a total of 8!

Noble Gases/Inert Gases

• Group # 18• All nonmetals• 8 valence electrons

- except helium only has 2.

• Unreactive– Have a full outer

electron level– 2 on the 1st level– 8 on the 2nd level

Hydrogen stands alone

1 valence electronVery reactiveColorless, odorless

gas at room temperature.

Low densityReacts explosively

with Oxygen