Elements to Compounds
NCSCOS 4.02
Big Picture (Slide # 2)

Elements are pure substances with only ONE
type of atom.

Most matter is a combination of
elements
Atoms  elements  molecules 
compounds
Vocab terms: compound, molecule,
chemical formula, subscript, ionic
bond, covalent bond
*2.1D – ELEMENTS combine to form
Compounds* (Slide # 3)

1) 2 or more DIFFERENT
elements

2) Held together by
CHEMICAL BONDS

3) The type of ATOM &
the BOND determine the
properties (small note
sheet)
Compounds….. (2nd note
sheet) Slide # 4
Important characteristics of COMPOUNDS:
1.
have a definite composition
2.
can be broken down into simpler
substances by chemical means
3.
can be identified by their physical
properties
4.
Compounds usually have very different
properties than the elements that compose
them
EX: Ca (soft, silvery metallic solid;
needed by humans); Cl (greenishyellow gas; poisonous to humans)
BUT..CaCl (nonpoisonous white
solid used to melt ice on streets) 
Molecules (small note sheet – Slide # 5)
Def: A group of atoms held
together by a covalent bond.
EX: Water
Molecules: Compounds
Atoms: Elements
*(note sheet)
Chemical formulas= use chemical
symbols and subscripts to show
how many atoms of those
elements are combined in the
compound (RATIO!)
Chemical Formulas
Slide # 6 
Formulas are written with chemical
symbols and subscripts which
indicate the # of times that
element appears in the molecule.
Elements without a subscript have
an imaginary “1”
H2O: subscript indicates 2 hydrogen
atoms and 1 oxygen atom (water)
CO2: 1 carbon with 2 Oxygen (carbon
dioxide)
C3H8: 3 carbon with 8
hydrogen(propane)
C6H12O6: 6 carbon, 12 hydrogen,
and 6 oxygen (glucose)
(go back to note sheet)
Fill in the Chart (pls place in
ntbk) (please just do a practice one in notebook
w/notes)
Compound
Na2SO4
Al2O3
CaSO4
C2H6
Fe
NH3
Symbol and # of Total # of
atoms
atoms
Na=2,S=1,O=4
7
Slide # * - 1st note sheet)
The
SAME elements
can be used to form
VERY DIFFERENT
compounds with
DIFFERENT
properties.
WATER vs
HYDROGEN
H2O
PEROXIDE
(small note sheet


2:1

Clear

Colorless

Odorless

Needed for Survival

H2O2

2:2

Clear

Colorless

Odorless

Thick, Syrupy

Kills Bacteria

Poisonous if ingested

Can be used as fuel
NO ( 1N , 1O)

NITROGEN & OXYGEN

Nitrogen Monoxide: By
product of combustion
of substances in air,
engine, fossil fuels,
power plants, lightning

Nitrous Dioxide: Brown
toxic gas, major air
pollutant, used in
racing

Nitrous Oxide: Used by
dentist, surgery as mild
anesthetic, greenhouse
gas

(just COOL INFO!!)
NO2 ( 1N , 2O)
N2O ( 2N, 1O)
N2O ~ Nitrous Oxide
2.2D
Chemical Bonds (1st
note sheet) Slide # 12
Chemical bonds are forces
(the “glue”) that hold
atoms together. 2
types:
1. Ionic Bonds: valence
electrons completely
transferred
2. Covalent bonds:
valence electrons
shared

Slide # 13

(Note sheet # 2)
IONIC BONDS
Attraction between (+) & (-) ions = ionic bonds
Ionic compounds are very stable & their strong crystal
structure
, shatters, separates into ions when
dissolved ; conduct electricity; high Boiling Point &
Melting point
* Naming ionic compounds – Positive Ion always named 1st


Negative Ion is named by dropping last part of name &
adding the suffix “ide ”
EX: Sodium Chloride (Na+Cl-)
PROPERTIES OF IONIC BONDS
(2nd note sheet) Slide # 14
IONIC BONDS….
*occur
when metals react with nonmetals
* hard (think of a LEGO structure)
*brittle
*high melting & boiling points
*transfer of electrons
*conduct electricity when dissolved in water
EX: salt, concrete, sulfuric acid
COVALENT BONDS (Slide #
15)
Electrons are SHARED…neither atom “loses or
gains”…SO…NO IONS are formed!
 SHARED ELECTRONS are attracted to both
positively charged nuclei
 EX: H2, N2, O2…..
 The # of covalent bonds an atom can form
depends on the # of electrons available for
sharing
 POLAR COVALENT: when electrons are shared
unequally (polar-anything that has 2 extremes)
 EX: H2O

PROPERTIES OF COVALENT
BONDS (Slide # 16)

COVALENT BONDS……
*electrons shared between nonmetal and nonmetal
*not hard (think of a plastic ball pit)…softer
*not brittle
*low melting & boiling points
*don’t conduct electricity well & usually don’t
dissolve in water; are usually more flammable
EX: O2, CO2, methane, hydrochloric acid, candy
corn
Atomic Theory
Proposed in 1808 by John
Dalton.
1.
2.
3.
All matter is
composed of atoms
Atoms of a given
element are identical
Atoms of different
elements combine in
simple, wholenumber ratios to form
chemical compounds
The FOLLOWING INFO…

For
LATER…ALLIGATOR 
3.3D-Chemical Reactions Involve
ENERGY Changes
 Bond
energy = energy
associated with bonds
between atoms
 Breaking bonds uses
(requires) energy
 Forming bonds gives off
(releases) energy
IF……


More energy is RELEASED than added
EXOTHERMIC REACTION
Reactants YIELD PRODUCTS + ENERGY
 (baggy of Yeast + Hydrogen Peroxide)



More energy is ABSORBED than
released
ENDOTHERMIC REACTION
Reactants + Energy YIELD PRODUCTS
 (baggy of Baking Soda + Vinegar)

Exothermic & Endothermic Reactions…
work together to CREATE SYSTEMS OR CYCLES!!

PHOTOSYNTHESIS = making glucose (sugar) & Oxygen

ENDOTHERMIC

6CO2 + 6H2O + Energy

CELLULAR RESPIRATION = reverse of photosynthesis,

EXOTHERMIC

C6H12O6 + 6O2
from Carbon Dioxide,Water & Energy
C6H12O6 + 6O2
the production of Carbon Dioxide, Water & Energy from
combustion of glucose, using Oxygen
6CO2 + 6H2O + Energy
Exothermic & Endothermic Reactions…
work together to CREATE SYSTEMS OR CYCLES!!

PHOTOSYNTHESIS = making glucose (sugar) & Oxygen

ENDOTHERMIC

6CO2 + 6H2O + Energy

CELLULAR RESPIRATION = reverse of photosynthesis,

EXOTHERMIC

C6H12O6 + 6O2
from Carbon Dioxide,Water & Energy
C6H12O6 + 6O2
the production of Carbon Dioxide, Water & Energy from
combustion of glucose, using Oxygen
6CO2 + 6H2O + Energy
REVIEW 
 CHEMICAL
HINTS….
 1)
REACTION
Temperature Change
 …Heat…Energy…Produced
 = ?
Answer:
FIRE
COMBUSTION
EXPLOSION
Your
shirt has
white spots
because you
dyed eggs using
vinegar?
Answer:
COLOR
CHANGE
BUBBLES
ARE
PRESENT???
Answer:
GAS
PRODUCED
Usually CO2
A
SOLID IS
FORMED….when
u started with
LIQUIDS????
Answer:
PRECIPITATE
ELEMENT!!!
Only
1 TYPE of ATOM!!
Compounds
A
compound is a pure
substance composed of 2 or
more elements that are
chemically combined
Examples of Compounds
elements
•The elements combine + lose their original properties
•Compounds CAN be separated by chemical means
• The elements combine in specific ratios
•Compounds contain
Sodium (Na)
+
Chlorine (Cl)
NaCl
Hydrogen (H) + Oxygen (O)
H2O
Carbon (C) + Oxygen (O)
CO2
Mixtures
A
mixture is a
combination of 2 or more
substances that are not
chemically combined
Examples of Mixtures
chicken noodle soup
salad
pizza – yes, that would be Yoda…
Properties of Mixtures:
•Each substance in a mixture keeps its identity
•You can physically separate them
•They also contain elements, compounds, or both
•And they can be formed using any ratio of
components
Mixtures may be homogeneous
or
heterogeneous

The prefix “homo” indicates the same

Homogeneous mixtures have the
same appearance and properties throughout the mixture

The prefix “hetero” indicates difference

Heterogeneous mixtures consist of visibly
different substances
MUCH Later….Gator!! 