7.4 Human Genetics and Pedigrees Bell Work. 7.4 Human Genetics and Pedigrees Bell Work.
Bell Work
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Transcript of Bell Work
Bell Work• What charges will each of the
following have as ions?BrSMgBaI
AlSrNPB
Physical Science – Lecture 39
Bonding
Octet Rule
• All elements want 8 electrons in their outer shell.
• They want 8 valence electrons to be complete.• Elements want valence electrons equal to
noble gases (group 8A)
• Only exception – Hydrogen and Helium only want 2.
Becoming a Noble Gas
• Elements can lose or gain electrons to become “noble like”.
• Loss of electrons = cation (+ charge)• Gain of electrons = anion (- charge)
Cations
• Elements lose electrons to become positive• Positive charge comes from an abundance of
protons.• For every electron lost, elements becomes +1.
Anions
• Elements gain electrons to become negative• Negative charge comes from an abundance of
electrons.• For every electron gained, elements becomes
-1.
Two types of Bonding - 1
• Covalent – between two non-metals. They share electrons.
• Two non-metals will share electrons to make them both think that they have a full outer shell.
Bonding - Covalent
Forming Covalent Compounds
• When elements covalently bond, they are given special names to designate how many of each element is present.
Covalent Bonding
• Formed between two non-metals. • Neither atom is "strong" enough to steal
electrons from the other.• Instead, they share their electrons from outer
molecular orbit with others to feel complete (8).
Covalent Bonding
• Elements can form single bonds, double bonds, or triple bonds with other elements.
• Bonds are represented with line drawn between two elements.
Single Bond
• Two electrons are shared between elements
Double Bond
• Four electrons are shared between elements
Triple Bond
• Six electrons are shared between elements
Counting to 8
• Each pair of electrons (lone pair) counts as 2 electrons toward the total of 8 for the element they are attached to.
• Each covalent bond (line) counts as 2 electrons for each element they are attached to.
• Everyone still wants 8.
Types of Bonding - 2
• Ionic – between a metal and a non-metal or a cation and an anion. They steal or give away electrons to each other.
• A metal will give its electrons to a non-metal to have a completed octet in the octet below its valence shell (becoming a cation).
• A non-metal will take electrons from a metal to fulfill its outer valence shell (becoming an anion).
Lone Pairs
• Electrons not involved in the bond are called “lone pairs”.
• Lone pairs consist of two electrons.
Ionic Bonding
• Ionic bond - type of bond formed between cations and anions.
• Mostly formed between metals and non-metals.
• Non-metals are more electronegative and steal the metals electrons.
Bonding - Ionic
Ionic Bonding
•Na does not have 8 electrons in its outer shell, it has none. •It gave away electrons. It did not share.
Ionic Bonding
• Metals NEVER keep their electrons! • They always give them away to non-metals.• They NEVER share!
Forming Ionic Compounds
• Ionic compounds come from ions.• The charges cancel out
• The cation (positive charged element) is written first in the formula.
• The anion is always written second.
Examples
• Ca2+ and SO42-
• Br- and Na+
• K+ and O2-
Can 3 Cl form a Covalent bond with P?
• What type of bond will they form?• Do they have enough electrons to make them
each feel like they have 8?
What is the structure for Water?
What about C and four F?
What about Ca and 2 Cl?
What about 2 Cl?
What about O bonded to O?
Double Bonds
What about N bonded to N?
CH4
Practice
NH3
BaBr2
SH2
S2