Transcript Atomic

Biology I
INTRO TO
CHEMISTRY
Matter
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Anything that occupies space and has mass.
Examples:
1. rock
2. wood
3. metal
4. air
Matter is divided into 3 states
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Solids have both a definite
volume & definite shape
(rock)
Liquids have a definite
volume but no definite
shape; they can be poured
(water)
Gases do not have a
definite volume or definite
shape, but they take
the volume & shape of their
container
Matter consist of atoms, which are the smallest
unit of matter that can’t be broken down.
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Most atoms consist of 3 particles:
Electrons---Protons---Neutrons
Components of an Atom
Component
Charge
Location
1. Proton
positive
nucleus
2. Neutron
neutral
nucleus
3. Electron
negative
around the nucleus
Atoms
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The simplest particle of an
element that retains all the
properties of that element
Properties of atoms
determine the structure and
properties of the matter they
compose
Our understanding of the
structure of atoms based on
scientific models not
observation
The Nucleus
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Central core
Consists of positive
charged protons and
neutral neutrons
Positively charged
Contains most of the
mass of the atom
The Protons
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All atoms of a given element have the same
number of protons
Number of protons called the atomic number
Number of protons balanced by an equal
number of negatively charged electrons
The Neutrons
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The number varies slightly among atoms of
the same element
The Electrons
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Negatively charged high energy particles
with little mass
Travel at very high speeds at various
distances (energy levels) from the nucleus
Chemical Elements
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Elements are pure substances which cannot be
chemically broken down into simpler kinds of
matter.
More than 100 elements have been identified,
but only about 30 are important in living things
All of the Elements are arranged on a chart
known as the Periodic Table
Periodic charts tell the atomic number, atomic
mass, & chemical symbol for every element
Four elements, Carbon – C, Hydrogen – H,
Oxygen – O, and Nitrogen – N make up almost
90% of the mass of living things
Chemical Elements cont..
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Each element has an unique chemical symbol
Consists of 1-2 letters
 First letter is always capitalized
The number of protons in an atom is called the atomic
number & determines which element it is.
 The number of protons & neutrons is called the atomic mass
or mass #.
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How do we find the #of neutrons?
Atomic mass (# of neutrons & protons)
- Atomic # (# of protons)
= # of neutrons
10
12
35
8
ELECTRONS
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The number of positively charged protons is balanced
by an equal number of negatively charged electrons
(e-).
Electrons at outer levels have more energy than those
in inner levels.
Each level or shell can only hold a certain # of eThe first level, nearest the nucleus can only hold two
electrons, the second and other outer levels can hold
up to eight electrons each.
A stable atom is an atom that has a full outer level
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Electrons in the same energy level are
approximately the same distance from
the nucleus
Outer energy levels have more energy
than inner levels
Each level holds only a certain number
of electrons
ATOMS
Compound
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Substance containing two or more elements.
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Example:
C6H12O6
(glucose - sugar)
6 - carbons
12 - hydrogen
6 - oxygen
Question:
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Answer the following questions about
C6H12O6
1. How many elements are involved?
2. How many atoms are involved?
Answer:
1. Elements - 3 (C, H, O)
2. Atoms - 24
Atom
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The smallest unit of matter that still
retains the properties of an element.
Carbon - Atom
Protons - 6
Neutrons
-6
Electrons- 6
Atomic Number
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Equals the number of protons within the
nucleus of an element.
Examples:
Hydrogen (H) - 1
Sodium (Na)
- 11
Carbon (C)
-6
Oxygen (O)
-8
Gold (Au)
- 79
Atomic Mass
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Equals the number of protons + neutrons.
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Examples:
Hydrogen (H)
- 1.0079
Sodium (Na)
- 23
Carbon (C) - 12
Oxygen (O) - 16
Gold (Au)
- 197
Charge of an Element
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Question: protons = electrons
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Answer:
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Question: protons  electrons
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Answer:
charge is neutral
the charge is either negative or
positive
Isotope
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Atoms of elements with different number of
neutrons.
Examples:
carbon - 12
carbon - 13
carbon - 14
Isotopes of Carbon
Nucleus
12C
13C
14C
protons
6
6
6
neutrons
6
7
8
electrons
6
6
6
Electrons
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orbit around the nucleus
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first bonding orbital - 2 electrons
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all other bonding orbitals - maximum 8 electrons
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orbitals have certain energy levels
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orbitals farther from the nucleus have the highest energy
level.
Sodium and Chlorine – Electrons
Bonding Orbitals
Na
Cl
Chemical Bonding
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Three types of bonds with different
strengths:
covalent > ionic > hydrogen
Covalent Bonds
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strongest bond
two elements share one or more pairs of
outer electrons
single and double bonds
+
H
Examples:
- H+
O
1. H2O (water - polar molecule)
H
2. CH4 (methane)
H-C-H
3. O2 (dioxide)
O=O
H
Ion
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atom or molecule with an electric charge.
resulting from a gain or loss of one or
more electrons.
Examples:
Sodium ion (Na+)
Chloride ion (Cl-)
Ionic Bonds
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second strongest bond
two ions with opposite charges attract
to each other.
Examples:
salts (NaCl)
acids
bases
Ionic Bond
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Example: salt (NaCl)
Na
Cl
Hydrogen Bonding
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weakest of the three bonds.
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Most important and common of all bonds.
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Partially positive hydrogen atom of one
molecule is attracted to the partially negative
atom of another molecule (O or N).
Example: H2O
hydrogen bonds
H+
O- H+
H+
O- H+
H+
O- H+
O- H+
H+