Atoms,Elements, and Compounds

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Atoms,Elements, and Compounds
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ATOMS

• Atoms are the basic building blocks of matter
  that make up everyday objects.
• A desk, the air, even you are made up of atoms!
• Matter- Anything that takes up space

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Parts of the Atom

• Electron negative particle circling the
  nucleus (each electron has a 1 charge)
• Proton positive particle found in the
  nucleus (each proton has a 1 charge
• Neutron neutral particle found in the nucleus
  (a neutron has no charge)

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Atomic Number

• The number of protons in an atom defines what
  element it is. 
• For example carbon atoms have six protons,
  hydrogen atoms have one, and oxygen atoms have
  eight. 
• The number of protons in an atom also determines
  the chemical behavior of the element.

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Carbon and the periodic table

• Carbon
• Atomic symbol C
• Atomic number 6
• Atomic Mass 12
• Atomic protons
• protonselectrons
• Atomic Weight weight of protons, neutrons, and
  electrons
• Electrons add little weight and are insignificant
  on a periodical table
• Protons and Neutrons weigh the same

Neutrons Atomic Weight (rounded) Atomic
number
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ELEMENTS

• substances that cannot be decomposed or broken
  into simpler substances by ordinary chemical
  means.
• Elements are made up of only one kind of atom
  ex. Carbon(C), oxygen(O2), helium(He)

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Element Name and Symbol

• Atomic SymbolThe atomic symbol is one or two
  letters chosen to represent an element ("H" for
  "hydrogen," etc.). 
• Memorize the symbols/ names of the following
• C Carbon
• O Oxygen
• H Hydrogen
• He Helium
• Na Sodium
• Fe Iron
• N Nitrogen
• S Sulfur

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Compounds

• Substance formed by a combination of two or more
  elements
• (ex. Water (H2O) has hydrogen and oxygen

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Mixtures/Solutions

• Mixture- Substances that do not dissolve together
  but mix
• Solutions Mixture that is evenly distributed
  throughout the solution

Solution
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Mixtures

• Solution
• Solute- NaCl
• Solvent- water

NaCl Dissolving in Water When an ionic compound
such as sodium chloride is placed in water, water
molecules surround and separate the positive and
negative ions.
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Mixtures

• Mixture
• Different particles not dissolved

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Atom vs. Molecule

• Atom the smallest possible particle of a
  molecule that retains its chemical properties
• Molecule - two or more atoms in a definite
  arrangement held together by chemical bonds

Example A Hydrogen Atom
Water is always H2O
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What is in a Molecule

• Formulas
• Subscript (Little number after an element symbol
  in a molecule) means there are that number of the
  previous Atom
• H2O Water
• 2 Hydrogen 1 Oxygen
• Ammonia NH3
• 1 Nitrogen 3 Hydrogen
• Sucrose C12H22O11
• Table Salt NaCl
• Sodium Bicarbonate NaHCO3

H2O
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Definitions
Bond - joins two atoms togetherThe Octet Rule-
Says that atoms tend to gain, lose or share
electrons so as to have eight electrons in their
outer electron shell. -To be stable atoms must
have their outer orbit filled. -Usually the
outer orbit holds 8 electrons -Hydrogen and
Helium have an outer orbit that only holds 2
electrons. Chemical bond a force that holds
two atoms together (occurs because atoms want to
achieve stability ) atoms want to have a complete
outermost energy level
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Types of bonds

• Ionic bonding bonding that involves a transfer
  of electrons (one atom gains electrons and one
  atom loses electrons) ions are formed
• Electrons have a -1 charge
• A positive ion is formed when a electron is given
  off
• A negative ion is formed when a electron is
  gained

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Types of Bonds

• Covalent bonding - occurs when atoms share
  electrons to fill outer orbits. Water is 2
  Hydrogen and 1 Oxygen covalently bonded.

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Covalent bonding

• Electrons in a covalently bonded compound are not
  shared equally
• Larger atoms tend to hog more electrons.
• In water Oxygen hogs
• more of the electrons and
• therefore the oxygen side
• is more negative and the
• hydrogen side is slightly
• positive
• -When there are different
• charged sides the molecule
• is said to be polar.

- side
side
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Hydrogen Bonds

• Attraction that forms between two polar molecules
  (when hydrogen is present).
• The positive side of one polar molecule attracts
  and is bonded to the negative side of another
  polar molecule.

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Compound

• A substance formed by the combination of two or
  more elements in definite proportions.
• Exp NaCl, Salt