2.1 nature of matter. atoms atoms are the basic unit of matter theorized by democritus, 2500 yrs ago...
TRANSCRIPT
2.1 Nature of Matter
Atoms• Atoms are the basic unit of matter
• Theorized by Democritus, 2500 yrs ago
• Composed of 3 subatomic particles– Protons– Neutrons– Electrons
Nucleus
• Center of the atom
• Made up of the protons and neutrons– Protons (+) charge– Neutrons (= or neutral) charge
• # of protons and neutrons make up the atomic mass number
Electrons• Very important in bonding with other elements• (-) charge• Attracted to the positively charged nucleus• Remains outside the nucleus in a cloud• Usually has the same number of electrons as
protons• Maintains electrically neutral atoms• Very small compared to protons and neutrons
Elements
• A pure substance that consists of entirely of one type of atom
• A list of all the elements can be found in the periodic table
Isotopes
• Elements which have different numbers of neutrons
• All isotopes have the same number of protons giving them the same properties
Isotopes• Can be radioactive- unstable nuclei that
breakdown over time
• Can be used for many things-– Dating materials– Detect and treat cancers– Kill bacteria
Chemical Compounds
• Substance formed by the chemical combination of two or more elements
• Always form in the same proportions– EX: H2O, CO2
• Chemical compounds have very different characteristics compared to their elemental components.
NaCl
• Sodium- silvery, white metal– Explosive, if exposed to oxygen
• Chlorine- poisonous green gas– Extremely harmful to humans
+ =
Chemical Bonds• Ionic and covalent bonds are the main types
of bonds • Ionic- forms between metals and nonmetals
– Forms through a transfer of electrons• Covalent- forms between two nonmetals
– Produced through a sharing of electrons