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Basic Chemistry. General Biology. Matter – Atoms and Elements. Living and nonliving things are all made up of matter . Matter is anything that has mass and takes up space. Made of particles called atoms . An atom is the most basic unit of matter.

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basic chemistry

Basic Chemistry

General Biology

matter atoms and elements
Matter – Atoms and Elements
  • Living and nonliving things are all made up of matter.
  • Matteris anything that has mass and takes up space. Made of particles called atoms. An atom is the most basic unit of matter.
  • Atoms make up elements (such as oxygen, hydrogen, etc.). An elementis a pure substance that consists entirely of one type of atom.
building blocks of living matter
Building blocks of Living Matter
  • C (Carbon)
  • H (Hydrogen)
  • O (Oxygen)
  • N (Nitrogen)

There are four main elements in the molecules that make up the bulk of living organisms.

the periodic table of elements
The Periodic Table of Elements
  • Elements can be abbreviated by symbols (H=hydrogen, S=sulfur)
  • Is an important resource developed as a result of many scientific discoveries which is crucial to the study of chemistry.
  • Each box belongs to one element. Contains symbol, atomic number, mass number. Can be used to predict how elements behave.
slide5

The Periodic Table of Elements

Online Periodic Table: www.webelements.com

what is an atom
What is an atom?
  • An atom is the smallest particle of an element which still has all the properties of that element.
slide8

The number of protons in an atom determines what element it is.

The arrangement of electrons determines how the atom behaves.

  • Atoms contain smaller (subatomic) particles:
    • protons (+)
    • neutrons (0)
    • electrons (-) (very light)
structure of the atom
Structure of the Atom
  • Protons and neutrons in the NUCLEUS
  • Electrons moving rapidly in ENERGY LEVELS surrounding the nucleus

Atoms have no charge because the number of protons and the number of electrons is equal. (=neutral).

how many electrons per energy level
How many electrons per energy level?

We will only deal with elements with atomic numbers between 1 and 20. For atoms with higher atomic numbers, the rules are a little more detailed.

  • The first energy level can hold a maximum of 2 electrons.
  • The second energy level can hold a maximum of 8 electrons.
  • The third energy level can hold a maximum of 8 electrons.
slide11
The number and arrangement of electrons in the VALENCE of an atom determines its reactivity or how it will interact with other atoms.
  • Because of this, some atoms are more reactive than others.
slide12

Column 1: Very reactive. Tend to lose 1 electron

Column 2: Tend to lose 2 electrons

Column 3: Tend to lose 3 electrons

Column 4: Tend to share electrons

Column 5: Tend to gain 3 electrons

Column 6: Tend to gain 2 electrons

Column 7: Very reactive. Tend to gain 1 electron

Column 8: NONREACTIVE – have either 2 or 8 electrons in valence.

bonds
Bonds
  • When the outermost (valence) electrons in one atom interact with the outermost (valence) electrons in another atom, they can form a BOND.
  • Atoms can form bonds with other atoms to become more stable.
  • Atoms may gain, lose or share electrons to become stable.
  • There are two major types of bonds:

a. Covalent bonds

b. Ionic bonds

vacancies
Vacancies
  • Electrons tend to “pair up” within each energy level.
  • Only the VALENCE (outermost level) energy level is available for bonding. Any “unpaired electrons” in the valence means a vacancy.
  • The number of vacancies = the number of bonds that atom can form.
  • Ex. Oxygen: has 2 vacancies in its valence; can form _2 bonds.
covalent bonds
Covalent Bonds

involve sharing electron(s) between two or more atoms.

a molecule is a grouping of atoms which have covalently bonded together.

covalently bonded molecules have no overall charge – they are neutral.

COVALENT BONDS
ionic bonds
IONIC BONDS
  • involve a transfer of electron(s) between two or more atoms.
  • After an atom gains or loses electron(s) it is called an ion.
  • An ionis an atom which has a positive or negative charge because it gained or lost electrons. The numbers of protons and electrons are no longer equal.
bohr models
Bohr Models
  • Show “rings” as energy levels
  • Put electrons in the energy levels (remember 2 – 8 – 8)
  • Put the number of neutrons and protons in the nucleus
lewis dot structures
Lewis Dot Structures
  • Write the element symbol
  • Put dots around the top, left, right, and bottom of the symbol showing the pairs of electrons in the valence only.
structural formulas
Structural Formulas
  • Show the atoms in a molecule using lines to represent covalent bonds.
molecular formulas
Molecular Formulas
  • A “shorthand” of symbols.
  • Use numbers as subscripts to tell how many atoms of each element.
  • Ex) H2O (water)
    • Contains 2 Hydrogen atoms and 1 Oxygen atom
  • Ex) C6H12O6 (glucose)
    • Contains 6 Carbon atoms, 12 Hydrogen atoms, and 6 Oxygen atoms
molecule
MOLECULE
  • One single unit of a compound is called a molecule of that compound. A molecule is the smallest unit of a compound that displays all the properties of that compound. A molecule can contain atoms which are alike or different.
compound
COMPOUND
  • Compound: a chemical combination of atoms from two or more different elements in definite proportions. Compounds can be very different from the elements that they are made of (ex., H and O vs. H2O).

O

H

H

chemical reactions
Chemical Reactions
  • Shown by an Equation.
    • Symbol = letter to represent an atom of an element
    • Chemical Formula = symbols and numbers to represent the name of a molecular compound
      • Numbers: Subscripts (little), Coefficients (big)
    • Chemical Name = words
    • Arrow () means “yields” (forms)
reactants react to produce products
Reactants react to produce products

Coefficient: How many of that molecule

Subscript: the number of atoms of that element in the molecule

Reactants: starting substances

Products: ending substances

subscript

energy the ability to do work
Energy – the ability to do work

Energy is used to break bonds in the reactant(s). Then atoms interact and rearrange, and energy is released when new bonds are formed in the product(s).

chemical reactions1
Chemical Reactions
  • Law of Conservation of matter governs chemical reactions.
    • Matter is neither created nor destroyed.
  • Reactants react to produce products
slide27
pH

pH is a measure of the acidity in a solution and is determined using a logarithmic scale.

Each number on the pH scale represents a 10-fold change in pH.

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