how atoms combine (7.3). atoms combine to become more ________. the most stable elements in the...
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How Atoms Combine (7.3)
• Atoms combine to become more ________.
• The most stable elements in the periodic table are the ___________________ because they have the maximum number of _____________ in their outermost orbits. (they have _____ valence electrons)
• There are 3 ways in which an atom that does not have a full valence shell can fill it:
1. it can __________ electrons,2. it can __________ electrons,3. it can __________ electrons.
All 3 methods result in the formation of a chemical ___________. A chemical bond is the attraction between 2 _________.
gainlose
share
atoms
stable
electrons8
Noble gases
bond
Ionic bond
covalent bond
IONIC COMPOUNDS(metals & non-metals)
IONIC BONDINGIonic bonds are formed between __________ elements and _____________ elements. Circle the compounds below that contain ionic bonds.
KCl H2O O2 MgO Na2S NH3 Cl2
Ionic bonds are formed by the attraction of 2 ____________ charged ions (an ion is a _________ particle).
metalnon-metal
oppositely charged
11 17
Example 1: Sodium (Na) and Chlorine (Cl)
Na Cl+ -
IONIC COMPOUNDS
IONIC BONDINGExample 1: Sodium (Na) and Chlorine (Cl)
• the sodium atom its outermost electron to chlorine so that both atoms get a full outer shell (and become ___________). Sodium has lost an electron and now has a _____________ charge, while chlorine has gained an electron and now has a _____________charge.
• ______________ charged atoms ___________, forming
an _____________ bond.
loses
stablepositive
negative
oppositely attract
ionic
IONIC BONDING
12
Example 2: Magnesium (Mg) and Fluorine (F)
Mg
F9
9 F
+-
-
+
IONIC BONDINGExample 2: Magnesium (Mg) and Fluorine (F)
• Magnesium needs to lose electrons. Fluorine needs
to gain electron. Magnesium can only lose two
electrons if it reacts with fluorine atoms.
• The formula for this compound is ___________
2
1
2
MgF2
Molecules & Covalent Bonding
Molecules & Covalent Bonding
• Covalent bonds are formed from ____________ elements.
• Unlike ionic bonds that are formed from ions that have ______ or ________ electrons, covalent bonds are formed from atoms that _______ electrons.
• The attraction of 2 atoms for the shared pair of electrons results in a __________ bond.
• Two or more atoms joined by covalent bonds form a __________.
non-metal
lost gainedshare
covalent
molecule
Molecules & Covalent Bonding
Example #1: Hydrogen MoleculeThe hydrogen molecule consists of 2 hydrogen atoms. Each hydrogen atom has _____ valence electron. If each atom shares its electron with the other atom, then each atom has _____ electrons in their outer shell (1st shell). The shell is now full and the atoms (and molecule) are ______________.
1
2
stable
The formula for a hydrogen molecule is .
Molecules & Covalent Bonding
H2
Bohr-Rutherford diagrams:
Electron Dot diagrams:
H H H H
Molecules & Covalent Bonding
Example #2: Hydrogen and ChlorineHydrogen and chlorine each need more electron in order to have a full shell. They do this by one pair of .
Electron Dot diagrams:
H Cl H Cl
The formula for the compound with hydrogen and chlorine is .
1
sharing electrons
HCl
Example #3: Hydrogen and Oxygen
Hydrogen needs more electron in order to have a full outer shell. Oxygen needs ____ more electrons to have a full outer shell. Oxygen can get a full shell if it shares its 2 unpaired electrons with hydrogen atoms. This also gives each hydrogen atom a full outer shell.
Molecules & Covalent Bonding
12
2
Molecules & Covalent Bonding
Electron Dot diagrams:
HO O H
H H
The formula for the compound with hydrogen and oxygen is . This compound is known as ________.
H2Owater
Molecules & Covalent Bonding
NOTE: When drawing electron dot diagrams for a molecule, use the stable octet rule. With the exception of hydrogen, each atom of the molecule should have 8 electrons (dots) surrounding it (including shared electrons).
IonicCompounds
Molecular (Covalent)Compounds
Type of Bonds ionic covalent
Types of Elements involved metals & non-metals non-metals only
State at 20C solid solids, liquids, gases
Forces between Ions or Molecules very strong weak
Melting & Boiling Points high relatively low
Solubility in Water soluble many are not soluble
Conducts Electricity?solid – no
liquids – yesdissolved in water - yes
no
ExamplesNaCl (salt)
CaOAgNO3
H2
H2OCCl4