Download 2.1 Atoms, Ions, and Molecules

2.1 Atoms, Ions, and Molecules
KEY CONCEPT
All living things are based on atoms and their
interactions.
2.1 Atoms, Ions, and Molecules
Living things consist of atoms of different elements.
• An atom is the smallest basic unit of matter.
• An element is one type of atom.
Hydrogen atom (H)
H
Oxygen atom (O)
O
2.1 Atoms, Ions, and Molecules
• An atom has a nucleus and electrons.
– The nucleus has
- Protons (+)
- Neutrons (0)
– Electrons (-) are in energy levels outside nucleus.
Oxygen atom (O)
Nucleus:
8 protons (+)
8 neutrons
outermost energy level:
6 electrons (-)
inner energy level:
2 electrons (-)
2.1
Atoms,
andTable
Molecules
Reading
theIons,
Periodic
• Atomic Number: Number • How many neutrons does
of protons (+)
Carbon contain?
determines the type of
atom
• Atomic Mass: Combined
protons and neutrons
inside the nucleus
2.1
Atoms,
What’s
the:Ions, and Molecules
A) Atomic number of
Beryllium?
4
B) Atomic mass of Beryllium?
9
C) How many protons?
4 (the atomic #)
D) How many electrons?
4 (protons & electrons usually equal)
E) How many neutrons?
5
(9 protons & neutrons – 4 protons = 5 neutrons)
2.1 Atoms, Ions, and Molecules
• Electrons orbit the nucleus
in “energy levels”
• 1st level: closest to nucleus
(holds 2 electrons)
• 2nd level: holds 8 electrons
• 3rd level: stable with 8
• Atoms are stable &
unreactive when the
outermost level is “full”
• Is the oxygen atom to the
right stable?
2.1 Atoms, Ions, and Molecules
• A compound is made of atoms of different elements
bonded together.
– water (H2O)
_
O
H
+
H
+
2.1 Atoms, Ions, and Molecules
• A compound is made of atoms of different elements
bonded together.
– water (H2O)
– carbon dioxide (CO2)
2.1 Atoms, Ions, and Molecules
Atoms share pairs of electrons in covalent bonds.
• A covalent bond forms when atoms share a pair of
electrons.
– multiple covalent bonds
– diatomic molecules
covalent bonds
Oxygen atom (O)
Carbon atom (C)
Carbon dioxide (CO2 )
Oxygen atom (O)
2.1 Atoms, Ions, and Molecules
Ions form when atoms gain or lose electrons.
• An ion is an atom that has gained or lost one or more
electrons.
One atom “steals”
– positive ions (+)
an e- from another
– negative ions (-)
• Ionic bonds form between oppositely charged ions, where
electrons are gained/lost.
gained electron
Na loses an
electron to CI
Sodium atom (Na)
Chlorine atom (CI)
ionic bond
Sodium ion (Na+)
Chloride ion (CI-)
2.1 Atoms, Ions, and Molecules
ee
ee
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ee
e
e
e
e
e
e
ee
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ee
ee
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e
ee
ee
• Ex: Sodium + Chlorine = Sodium Chloride
Na
= 11Molecules
Cl atomic number = 17
2.1 atomic
Atoms,number
Ions, and
Before the bonding
Na
Protons
(+)
Electron
s (-)
Net
charge
11+
110
After the bond
Cl
Na
Cl
17+
Protons
(+)
11+
17+
17-
Electron
s (-)
10-
18-
0
Net
charge
+1
-1
2.1 Atoms, Ions, and Molecules
Quick
Review
• Atoms become stable when their outer
electron level is “full”
• Molecules created when 2 or more
atoms combine together
• Covalent Molecules: share electrons
• Ions: lose and gain electrons