CH2 Sec1

Matter and Substances

• Everything is made up of matter.

• Matter is anything that has mass and takes up space.

• Matter is made up of Atoms • Atoms are the smallest unit of matter • Atoms have positively charged center (core)

surrounded my negatively charged region

Atomic StructureMade up of three kinds of particles:

Protons – (+) positively charged

Electrons – (-) negatively charged

Neutrons – No charge

•Protons and neutrons make up the core (center or nucleus)

•Electrons move around the nucleus in an electron cloud

Elements• Are made up of atoms that have the same

number of protons– Elements found within the same column have

similar properties

• Isotopes are atoms of an element that have

different numbers of neutrons

Periodic Table

Determining # of electrons, protons, and neutrons in atom

• Atomic # = # protons• Protons = electrons• Atomic mass = p + n

Determining # of electrons, protons, and neutrons in atom

• Atomic # = # protons (27)• Protons = electrons (27)• Atomic mass = p + n– 32 neutrons

• Now you try a few….

Chemical Bonds

• Electron cloud of an atom may have levels

• Innermost level can hold only 2 electrons • Levels farther from the nucleus can usually hold 8

electrons • Electrons in the outermost level (shell) are called

valence electrons, this is where atoms bind

Chemical Bonds• Opposites attract• Atoms come together and form a chemical bond• Making the atoms more stable they want an even number

of electrons in each level, forming a neutral charge

• A compound are created when atoms from two or more different elements bond

• Ions are atoms that have a + or - charge as a result of

gaining or losing electrons

Covalent Bond Ionic BondElectron pairs are shared

Molecules are produced

Bond is the attraction for shared electrons

Example: Water Molecule H20

Electrons are transferred

Ions are produced

Bond is the attractions between ions of the opposite chargeExample: Table Salt Na+Cl-

Covalent Bond and Ionic Bond

Table salt is an Ionic Compound because the positive Na (sodium) ion loses an electron to negative Cl (chloride) ion. Positive to Negative.

+

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Polarity

• Molecules charges on opposite ends are polar– One end is positive the other opposite end is

negative.

Solubility• Polar molecules that attract opposite charges• Water dissolves polar molecules such as salt

and sugar – Nature’s Solvent

• Not able to break the bonds of non-polar substances like wax, oil, or grease– Important characteristic of our cell membranes

Hydrogen Bonds• Play important role• Holds DNA strands together

• Type of weak covalent bond