10/3/14 objective: what are elements, compounds, and atoms? do now: give an example of “matter.”...
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10/3/14
Objective: What are elements, compounds, and atoms?
Do Now: Give an example of “matter.”
Chapter 4: The Chemical Basis of Life
Matter: Anything that occupies space and has mass
Element: Pure substance that cannot be broken down into other substances
Ex: Carbon (C), Hydrogen (H), Gold (Au)4 most common elements in living matter (96% of our body):
carbon (C), oxygen (O), hydrogen (H), nitrogen (N)
Trace Element: elements that make up less than 0.01 percent of your body, but are critical to life
Ex: iron
Compound: 2 or more elements chemically combined
Ex. Carbon dioxide(CO2), water(H2O)
Atomsatom: smallest possible particle
of an elementMade up of :Nucleus: central core of atom that contains
protons: single unit of positive electrical charge (+) neutrons: electrically neutral = no charge
Electrons: single unit of negative electrical charge (-) located outside of the nucleus
Why do you think the electrons remain close to the nucleus?
Atomic number: number of protons in an atom– Differentiates elements
Carbon Potassium
Atomic Weight (Mass number): # of protons + # of neutrons
Isotopes
• Isotope: same number of protons but different number of neutrons– Can make an element
radioactive– ex: 12C = normal, 14C
=radioactive
• Radioactive Isotope: nucleus decays over time giving off radiation in the form of matter and energy– ex. Carbon dating
Energy Levels• The electrons in an atom
determine how it will react with other atoms
• Electrons are found in clouds outside the nucleus
• Energy Levels– First level = lowest, nearest to
nucleus can hold 2 electrons– Second level = can hold 8
electrons– Most reactive when they have
partially full energy levels Nitrogen
Chemically reactive or Inert (doesn’t react)?
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