Post on 18-Jan-2016
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