Atomic Structure

The Atoms Family Atom: the smallest part of an element. Name means “indivisible”

Who’s atom is it? Dalton (bb) Rutherford Electron cloud model Thompson (Plum Pudding) Bohr (planetary) Standard Model

Parts of an Atom Nucleus:The main center of an atom. Made up of protons and neutrons Proton:In the nucleus. Has a + charge. Atomic number tells the number of protons Neutron:In the nucleus. Has NO charge. Is there to keep protons apart

Parts of an ATOM Electrons: In the electron cloud, has a negative charge.

The Same, But Different Isotopes:An element with different numbers of neutrons. Atomic mass - atomic number = number of neutrons. Example: Hydrogen 3 3(mass) - 1 (atomic #) = 2 neutrons Having an unequal number of neutrons and protons can make an atom unstable!

B. Subatomic Particles Most of the atom’s mass. Atomic Number NUCLEUS ELECTRONS PROTONS NEUTRONS NEGATIVE CHARGE POSITIVE CHARGE NEUTRAL CHARGE Most of the atom’s mass. Atomic Number equals the # of...

Let’s review Name the two sub-atomic particles found in the nucleus of an atom: Proton and Neutron What is the charge of a proton? Positive What is the charge of a neutron? No charge (neutral) Where are the electrons at? Orbiting the nucleus

II. Electron Cloud Model Orbital Energy Levels Bohr Model Diagrams Atomic Structure II. Electron Cloud Model Orbital Energy Levels Bohr Model Diagrams

Niels Bohr (1913) Bright-Line Spectrum tried to explain presence of specific colors in hydrogen’s spectrum Energy Levels electrons can only exist in specific energy states Planetary Model Niels Bohr (1913)

Demonstration Time

Niels Bohr (1913) Planetary Model: Bright-line spectrum Planetary Model: electrons move in circular orbits within specific energy levels

electron shells Electrons different amounts of energy and at different energy levels or electron shells. Electron shells (levels) determine… how an atom behaves when it encounters other atoms

Levels 1st Level: closest to nucleus. Has 1 orbital. Can hold 2 electrons 2nd level: next one out. Has 2 orbitals. Can hold 8 electrons. 3rd level: Holds 8 electrons. 4th level: Holds 18 electrons

Why are electrons important? Elements have different electron configurations so different levels of bonding Valence electrons are the electrons in the outer most shell. Valence electrons are important because they affect how the element reacts with other elements.

How many valence electrons are in these different atoms?

Octet Rule = atoms tend to gain, lose or share electrons so as to have 8 electrons C would like to N would like to O would like to Gain 4 electrons Gain 3 electrons Gain 2 electrons

Ne C. Stability Octet Rule most atoms form bonds in order to have 8 valence e- full outer energy level like the Noble Gases! Ne Stability is the driving force behind bond formation!

Electron Dot Structures Symbols of atoms with dots to represent the valence-shell electrons 1 2 13 14 15 16 17 18 H He:            Li Be  B   C   N   O  : F  :Ne :                    Na Mg  Al  Si  P S :Cl  :Ar :        

Learning Check A. X would be the electron dot formula for  A. X would be the electron dot formula for 1) Na 2) K 3) Al   B.  X  would be the electron dot formula 1) B 2) N 3) P

Stability Why is it important for an atom to be “stable”? So it is less reactive. Why are noble gases stable? They have a full energy level.