Atomic Structure

Nucleus Electron cloud An atom has two main parts.

Atomic Structure Atoms are composed of 3 subatomic particles: protons, neutrons, and electrons. The protons and neutrons are located in the nucleus of the atom. The electrons are located in a cloud surrounding the nucleus.

What makes up the nucleus? p n protons neutrons p n

Electrons are found orbiting outside the nucleus.

Atomic Structure Each subatomic particle has a charge associated with it. Protons = positive charge Neutrons = neutral charge (no charge) Electrons = negative charge

Atomic Number Atomic number number of protons  In a neutral atom p + = e - Oxygen 8 O

Atomic Number Oxygen 8 O NEUTRONS = atomic mass – atomic number

Periodic Table

Why does the periodic table look like this?

Periodic Trends Atomic mass increases as you move right and down Atomic size increases as you move right and down Elements of a period are listed consecutively in order of increasing atomic number

HHe LiBeBCNOFNe NaMgAlSiPSClAr KCaScTiVCrMnFeCoNiCuZnGaGeAsSeBrKr RbSrYZrNbMoTcRuRhRdAgCdInSnSbTeIXe CsBaLuHfTaWReOsIrPtAuHgTlPbBiPoAtRn FrRaLr The Periodic Table is broken into three basic categories of elements: Metals Nonmetals Metalloids

Metals Good conductors of heat and electricity Solid at room temperature (except for Mercury)

Non-metals Located on the right side of the periodic table (except for Hydrogen) Usually found as a gas at room temperature Do not conduct heat or electricity well The noble gases are the only group that contains ALL non-metals

Metalloids Can have both metallic and non-metallic properties Are found along the stair- step…

vertical columns are called GroupsGroups HHe LiBeBCNOFNe NaMgAlSiPSClAr KCaScTiVCrMnFeCoNiCuZnGaGeAsSeBrKr RbSrYZrNbMoTcRuRhRdAgCdInSnSbTeIXe CsBaLuHfTaWReOsIrPtAuHgTlPbBiPoAtRn FrRaLr Atoms increase in size descending through a group valence electrons Atoms in a group have the same number of valence electrons so they have similar properties

HHe LiBeBCNOFNe NaMgAlSiPSClAr KCaScTiVCrMnFeCoNiCuZnGaGeAsSeBrKr RbSrYZrNbMoTcRuRhRdAgCdInSnSbTeIXe CsBaLuHfTaWReOsIrPtAuHgTlPbBiPoAtRn FrRaLr Many groups have special names that describe their characteristics: Alkali Metals Halogens Alkaline Earth Metals Transition Metals Noble Gases

Transition elements Elements found in the middle block of the periodic table The Lanthanide and Actinide series are the two rows at the bottom of the table.

Alkali Metals Elements found in Group 1A Most reactive of all metals Each alkali metal has one valence electron

Alkaline Earth Metals Elements found in Group 2A Combine readily with other elements Each alkaline earth metal has 2 valence electrons

Halogens Elements found in Group 7A Very reactive elements Each halogen has 7 valence electrons

Noble Gases Elements found in Group 8A Very stable because their outer energy level is full Each noble gas has 8 valence electrons

Periods The horizontal rows on the periodic table are called periods. There are 7 periods on the table.

HHe LiBeBCNOFNe NaMgAlSiPSClAr KCaScTiVCrMnFeCoNiCuZnGaGeAsSeBrKr RbSrYZrNbMoTcRuRhRdAgCdInSnSbTeIXe CsBaLuHfTaWReOsIrPtAuHgTlPbBiPoAtRn FrRaLr Horizontal rows are called Periods and demonstrate trends as well. Atoms increase in size ascending through a period Atoms in a period have the same number of electron shells Periods

Oxygen 8 O Group # Period # # of Valence Electrons Metal, nonmetal, metalloid? To the left of each box, make sure to also include:

Bohr Models Bohr models are models of atoms where the electrons are placed in energy levels. Reminder: level one holds up to two electrons. Levels two and three hold up to eight.

Bohr model relates to periodic table The first period on the table has two elements…and the first energy level holds two electrons. The second period has eight elements…and the second energy level holds eight electrons.

Bohr model relates to periodic table Period determines the number of energy levels. Group determines the number of electrons in the valence shell.

Bohr model of Carbon

Bohr Model of Carbon

Reminders: Valence electrons – electrons in the outer energy level of an atom Mass number – number of protons plus neutrons in the nucleus of a particular kind of atom Atomic number – the number of protons in a particular kind of atom