Bio Chapter 2
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What is matter?
Anything that has mass and occupies space.
What is an Element?
- Purest form of a substance
- Has one kind of atom
Water makes up about how much of our body weight?
Water makes up about 70% of our body weight!
What 4 major elements make up ~96.3% of our body?
List by highest percentage.
- Oxygen 65.0%
- Carbon 18.5%
- Hydrogen 9.5%
- Nitrogen 3.3%
What is a compound?
consists of two or more different elements combined in a fixed ratio
Ex: H2O (2:1 ratio) , NaCl (1:1 ratio)
Out of the 92 natural elements, about __________ % are _________ elements that an organism needs.
Out of the 92 natural elements, about 20-25% are essential elements that an organism needs.
How many elements do humans need?
How many elements do plants need?
Humans need 25 elements
Plants need only 17 elements
What elements make up ~4% of our body?
- 1. Ca
- 2. P
- 3. K
- 4. S
- 5. Na
- 6. Cl
- 7. Mg
What are the 3 SUBATOMIC particles?
What is located in the nucleus of an atom?
Protons and Neutrons
What is located outside of the nucleus of an atom?
A "cloud" made up of electrons
What is an isotope?
Same element but diff. # of Neutrons.
- P+ mass is 1
- E- mass is 0
- N mass is 1
What is an Atomic Number?
Number of PROTONS
What is a Mass Number?
Mass # = Protons + Neutrons
Define Potential Energy.
Energy that matter possess because of location or structure.
The more distant an electron is from the nucleus the greater its ________ energy.
It takes more work to move e- farther from the nucleus.
The first shell has the _______ energy level.
First shell is closest to the nucleus so e- have lowest potential energy.
Chemical behavior of an atom depends mostly on the # of -e in its ________shell.
What are valence electrons?
E- located in the outermost shell of an atom
Outermost shell=valence shell
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