Valence Electrons and Bonding The number of valence electrons electrons in the outermost energy level in an atom of an element determines many properties of that element including the ways in which the atom can bond with other atoms ID: 356342
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Slide1
Atoms, Bonding, and the Periodic Table
Valence Electrons and Bonding
The number of valence electrons (electrons in the outermost energy level) in an atom of an element determines many properties of that element, including the ways in which the atom can bond with other atoms.Slide2
The Periodic TableAs the number of protons (atomic number) increases, the number of electrons also increases. As a result, the properties of the elements change in a regular way across a period.
The maximum # of
outermost
electrons an atom can have is eight (even if the energy level could otherwise hold more).Slide3
Why are noble gases relatively UNreactive?
Question:Slide4
Why are noble gases relatively UNreactive?
Question:
Their atoms already have eight outermost electrons, so they are stable. Slide5
Charged Particles
Sometimes an atom can gain or lose electrons
When the # of electrons is different from the # of protons, then the atom has an electrical charge.These atoms are called ions.Slide6
- Ionic Bonds
Ions and Ionic Bonds
When an atom loses an electron, it loses a negative charge and become a positive ion. When an atom gains an electron, it gains a negative charge and becomes a negative ion.Slide7
Ionic Bonds
A bond that forms when one atom takes one or more electrons from another atom is called an ionic bond
. One atom gains electrons (becomes -); the other atom loses electrons (becomes +).
The opposite charges (+/-) attract.Slide8
Question:
Does a negative ion have more protons or more electrons?Slide9
Question:
Does a negative ion have more protons or more electrons?
Answer: More ELECTRONS!Slide10
Ionic Bonding with Sodium and Chlorine
Slide11
- Ionic Bonds
Ions and Ionic Bonds
Ionic bonds form as a result of the attraction between positive and negative ions.Slide12
- Ionic Bonds
Properties of Ionic Compounds
In general, ionic compounds are hard, brittle crystals that have high melting points. When dissolved in water or melted, they conduct electricity.Slide13
Nomenclature
We write ions with their chemical symbol, then with a + or – the number of electrons lost or gained.
A “+” charge indicates the # of electrons lost
A “-” charge indicates the # of electrons gained.Slide14
- Ionic Bonds
Ions and Ionic Bonds
Ions are atoms that have lost or gained electrons.Slide15
Check Questions
Formation of an Ionic Bond
Q
. What is an ionic bond?
A
. An ionic bond is the attraction between two oppositely charged ions.
Q
. What is the overall charge on an ionic compound?
A
. Overall, an ionic compound is electrically neutral.
- Ionic BondsSlide16
End of Section:Ionic BondsSlide17
Covalent Bonding
"
My name is Bond… Covalent Bond."Slide18
Covalent Bonding
A bond formed when atoms share electrons
Let’s fill in the blanks:An atom wants to fill its outermost energy level with _______ electrons, unless they are the elements _________ or ________, which only want ____. Slide19
Covalent Bonding
A bond formed when atoms share electrons
Let’s fill in the blanks:An atom wants to fill its outermost energy level with _eight__
electrons, unless they are the elements _________ or ________, which only want ____. Slide20
Covalent Bonding
A bond formed when atoms share electrons
Let’s fill in the blanks:An atom wants to fill its outermost energy level with _eight__
electrons, unless they are the elements _
Hydrogen_
or _
Helium
_, which only want ____. Slide21
Covalent Bonding
A bond formed when atoms share electrons
Let’s fill in the blanks:An atom wants to fill its outermost energy level with _eight__
electrons, unless they are the elements _
Hydrogen_
or _
Helium
_, which only want
two_. Slide22
- Covalent Bonds
How Covalent Bonds Form
The force that holds atoms together in a covalent bond is the attraction of each atom’s nucleus for the shared pair of electrons.Slide23
- Covalent Bonds
How Covalent Bonds Form
The oxygen atom in water and the nitrogen atom in ammonia are each surrounded by eight electrons as a result of sharing electrons with hydrogen atoms.Slide24
- Covalent Bonds
How Covalent Bonds Form
An oxygen molecule contains one double bond, while a carbon dioxide molecule has two double bonds. A nitrogen molecule contains one triple bond.Slide25
- Covalent Bonds
Unequal Sharing of Electrons
Fluorine forms a nonpolar bond with another fluorine atom. In hydrogen fluoride, fluorine attracts electrons more strongly than hydrogen does, so the bond formed is polar.Slide26
- Covalent Bonds
Unequal Sharing of Electrons
A carbon dioxide molecule is a nonpolar molecule because of its straight-line shape. In contrast, a water molecule is a polar molecule because of its bent shape.Slide27
Question
Answer
Asking Questions
How do covalent bonds form?
Covalent bonds form when two atoms share electrons.
How does unequal sharing of electrons affect the atoms in molecular compounds?
Unequal sharing of electrons causes the bonded atoms to have slight electrical charges.
- Covalent BondsSlide28
End of Section:Covalent BondsSlide29
- Bonding in Metals
Metallic Bonding
A metal crystal consists of positively charged metal ions embedded in a “sea” of valence electrons.Slide30
- Bonding in Metals
Metallic Properties
The “sea of electrons” model of solid metals explains their ability to conduct heat and electricity, the ease with which they can be made to change shape, and their luster.Slide31
Properties of Metals due to Metallic Bonding
Metallic bonding
Electrical conductivity
Heat conductivity
Ductility
Malleability
Luster
Cause
Effects
- Bonding in MetalsSlide32
End of Section:Bonding in MetalsSlide33
Graphic Organizer
Attraction between opposite (+/-) ions
Feature
Ionic Bond
Polar Covalent Bond
Nonpolar Covalent Bond
Metallic Bond
How Bond Forms
Charge on Bonded Atoms?
Example
Unequal
sharing
of electrons
Yes; positive or negative
Yes; positive
because the electrons are only loosely connected
O
2
Equal
sharing
of electrons
Attraction between positive ions and “sea” of electrons.
Yes, slightly positive or slightly negative
No
Na
+
Cl
-
H
2
O
Gold