Transcript Elements and Compounds

Elements
• It has to be on the Periodic Table.
• Elements are “pure” meaning they cannot
be broken down chemically.
Periodic Table
• period
• group
• Group 1: alkalis
• Group 17: halogens
• Group 18: Noble Gases
Atomic Math
• Atomic number = the number of protons
• Atomic mass = # of protons + # of neutrons
o So # neutrons =?
Element vs. Compound
• Elements
• Compounds
• found in nature
• is on the Periodic Table of the
Elements
• contains only 1 element
• some needed for life
• smallest part of an element is an
atom
• found in nature
• Examples: carbon, oxygen, iron
• has 2 or more elements
• some needed for life
• smallest part of a compound is a
molecule
• created by a chemical reaction
• Examples: water, carbon
dioxide
Examples of Chemical Properties
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flammability (it can burn)
reactivity to oxygen (corrosion)
reactivity to light
reactivity to water
reactivity to electricity
reactivity to acid
Signs of a Chemical Change
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releasing a gas, bubbling
a change in temperature
forming a precipitate (a solid)
a change in color
reacting with oxygen (burning or rusting)
giving off light
making a noise (explosion)
not reversible
Law of Conservation of Mass
• Says the total mass before the reaction is the
same as the total mass afterwards.
• No matter is created or destroyed in a
chemical reaction!
Drawing an Atom!
• The atomic number = # of protons = # of electrons
• The atomic mass = total # of protons and neutrons in
nucleus.
• Step 1: Find the atomic mass for your element. Draw that
many circles for your nucleus. Pack them close together!
• Step 2: Find the atomic # for your element. Color that
many circles for your protons. Spread them around the
entire nucleus.
• Step 3: Color the rest of your nucleus as neutrons.
• Step 4: Draw the electrons around the nucleus, completely
surrounding it. The number is the same as the number of
protons.