BIO 120 Lecture Notes - Lecture 2: Atomic Nucleus, Radiometric Dating, Atomic Mass

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3 May 2018
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Bio 120- Chapter 2- Chemical Content of Life

1. Matter: make up organisms, which is anything that takes up space and
has mass. Can take on many forms: rocks, metals, oils, gases etc.
2. Elements: substance that cannot be broken down to other substances
by chemical reactions
a. 92 elements occurring in nature
b. Essential elements: 20-25% elements that an organism needs to
live a healthy life and reproduce
c. Oxygen, Carbon, Hydrogen, and Nitrogen approx 96% make up
living matter
d. Trace elements: required by an organism in only minute
quantities. Ex: iron, iodine
3. Compound: substance consisting of two or more different elements
combined in a fixed ratio. Example: NaCl- table salt
4. Atom: is the smallest unit of matter that still retains the properties of
an element.
a. Protons- positive, neutrons- neutral , and electrons- negative
b. Atomic nucleus: dense core at the center of an atom; protons=
positive charge, electrons- a cloud of negative charge around
nucleus and its attraction between opp charges keeps electrons
in cloud--Neutrons and protons have masses close to 1 dalton.
Electrons- do not account for total mass
5. Atomic number: This number of protons, which is unique to that
element, can be found as a subscript to the left of the symbol for the
element.
6. Mass number: total number of protons and neutrons in the nucleus of
the atom, subscript to the left of the elements symbol
7. Atomic mass: total mass of an atom
8. Isotopes: different atomic forms of the same element.
a. Radioactive: one in which the nucleus decays spontaneously,
giving off particles and energy- can be used as diagnostic tools
in medicine
9. Half Life: A “parent” isotope decays into its “daughter” isotope at a
fixed rate, —the time it takes for 50% of the parent isotope to decay.
10. Radiometric dating: scientists measure the ratio of different isotopes
and calculate how many half-lives (in years) have passed since an
organism was fossilized or a rock was formed.
11. Energy: capacity to cause change, doing work
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Document Summary

Bio (cid:327)(cid:328)(cid:326)- chapter (cid:328)- chemical content of life (cid:327). Matter: make up organisms, which is anything that takes up space and has mass. Can take on many forms: rocks, metals, oils, gases etc. (cid:328). Compound: substance consisting of two or more different elements combined in a fixed ratio. Electrons- do not account for total mass (cid:331). Atomic number: this number of protons, which is unique to that element, can be found as a subscript to the left of the symbol for the element. (cid:332). Mass number: total number of protons and neutrons in the nucleus of the atom, subscript to the left of the elements symbol (cid:334). Atomic mass: total mass of an atom (cid:335). Radiometric dating: scientists measure the ratio of different isotopes and calculate how many half-lives (cid:345)in years(cid:346) have passed since an organism was fossilized or a rock was formed. (cid:327)(cid:327).

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