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Protons•Positively charged•Found in the nucleus•Identifies element•Gives the element its atomic number•Gives nucleus its positive charge•Contributes to the atom’s reactivity• +
ELECTRONSoNegatively chargedoFound on the energy shellsoDetermines the reactivity of the atomoHas very small mass-not normally considered when calculating mass of atom.o e
Elements can be classified as
Metals: found on the left side of the periodic table less than 4 valence electrons
solids at room temperature
Nonmetals: found on the right side of the periodic table
more than 4 valence electronsgases at room temperature
Noble gases: found in the last column unreactive under normal situations gases at room temperature
Nucleus: protons and neutrons
+= n=
K shell: holds2 electrons
L shell: holds 8 electrons
M shell: holds 8 electrons(can hold up to 18 electrons)
Lithium
• Bohr model
Atomic mass = 7Atomic number = 3
= 3
n = 4
e = 3
++
n 4
3
Electron configuration: 2-1
Electron dot diagram is a way of representingonly the outer most shell. This shell is calledthe valence shell, is often unstable, and will be the shell involved in bonding.
Li F
What can we tell about an atom if we know atomicNumber and mass?
Atomic mass 14 atomic number 7
= 7 electron configuration = 2-5
n = 7 e dot = N
e = 7
Element is a nonmetal
+
+ = 7n=7
Elements can be classified as
Metals: found on the left side of the periodic table less than 4 valence electrons
solids at room temperature
Nonmetals: found on the right side of the periodic table
more than 4 valence electronsgases at room temperature
Noble gases: found in the last column unreactive under normal situations gases at room temperature
Periodic table arranges elements according to
atomic numberatomic number increases by one as
we read from left to right atomic number will determine
reactivity
Remember, valence means having to do withthe last shell.
Atoms like to use the least amount of energy.that means, they like to have their electronspaired and to have the valence shell stable with 8 electrons.
There are only 6 elements that naturally existin this stable state. They are …….
Noble gases
Atoms that are not stable cause trouble –they can be flammable, explosive, toxic.These problems are what make an atomreactive – meaning they want to becomestable. Bonding:
Ionic loss or gain of electronsCovalent sharing of electrons
IONIC BONDING: OCCURS BETWEEN-
METALS: LESS THAN 4 VALENCE ELECTRONSAND
NONMETALS: MORE THAN 4 VALENCE ELECTRONS
***REMEMBER: ATOMS WANT TO USE LITTLE E!!
METALS WILL LOSE ELECTRONSNONMETALS WILL GAIN THOSE ELECTRONS LOST
Ionic Bonding: occurs between metal and nonmetal
> 4 val. e < 4 val. E
lose e gain eform ions – charged atoms because
the # of protons does NOTequal # electrons.
+ ion - ion
Bonding between atoms is a result of:a. atoms need to be stableb. atoms need to exist in a lower
energy statec. attraction of positive nucleus and
negative electronsd. size of the atom’s radius
Atomic radius=distance betweennucleus and valence shell.the + nucleus will hold the – electronson the atom by means of attractiveforces. As atomic radius gets larger, attractive forces get smaller – electronslost easily. That’s good for a metal.as atomic radius gets smaller, attractiveforces get stronger. That’s good for anonmetal.
COVALENT BONDINGSHARING OF ELECTRONSATOMS REMAIN NEUTRAL
OCCURS BETWEEN:2 NONMETALS
A NONMETAL AND A METALLOIDHYDROGEN AND ALL NONMETALS
PRODUCES WEAK BONDSPRODUCES COMPOUNDS THAT HAVE LOW
MELTING POINTSALL ORGANIC COMPOUNDS ARE COVALENT
COVALENT BONDSBetween hydrogen and A nonmetal
Fluorine has 7 valence electronsIt needs 8 in order to exist in a lowerEnergy state. It could bond ionically With A metal or covalently with hydrogenby sharing one of its valence electrons.
Hydrogen has only one Electron and therefore will neverLose that electron. In order forIt to become stable and existIn a lower energy state, it willShare its only electron withfluorine
COVALENT BONDINGBETWEEN2 NONMETALS
Nonmetals, because they have more than 4 valence electrons and especially those that have small atomic radii, will bond with them-selves in order to become stable and exist at a lower energy state.
These atoms will be called DIATOMS. There are 7 diatomsThat you will need to memorize. They are F, Cl, Br, I, O, N, H.
COVALENT BONDINGBETWEEN
NONMETAL AND A METALLOIDCarbon will be our only metalloid with 4 valence electrons
Fluorine is a Nonmetal with 7 Valence electrons
The resulting stable cmpdContains 4 F and 1 C. Because the atoms never LOST E’s they remainneutral.
Comparison of bonds
• Ionic Bonding: • occurs between metal
and nonmetal• lose e gain e• form ions – charged
atoms
• COVALENT BONDING SHARING OF ELECTRONS
ATOMS REMAIN NEUTRAL
OCCURS BETWEEN: 2 NONMETALS
A NONMETAL AND A METALLOID
HYDROGEN AND ALL NONMETALS
POLARITYUNEVEN DISTRIBUTION OF CHARGES
__ +
On polar molecules, electrons are controlled by oneOf the atoms.