Questions
1) How a chemical connection to biology? (use a example)
The example in the book talked about the “devil’s gardens” In this forest, there’re just one kind of
trees, and they are well organized. Then scientists find out there’re a kind of ants they express a
poisonous chemical to stop other kinds of trees living in the forest. So in this forest, there’s just one
kind of tree called Duroia hirsute. From this case, we can see the chemical connection to biology.
2) What’re the main elements which make up 96% of living matter?
Carbon, oxygen, hydrogen, nitrogen
3) What’re the three kinds of subatomic particles?
Neutrons, protons, electrons.
The facts
1) The more distant an electron is from the nucleus, the greater its potential energy.
2) Atom is composed of subatomic particles.
3) Covalent bond, double covalent, hydrogen bond, van der waals interactions are all chemical
bonds.
4) All atoms of a particular element have the same number of protons in their nuclei.
5) Chemical reactions make and break chemical bonds.
Summary：
Matter consists of chemical elements in pure form and in combinations called compounds. Matter is made up of elements, and element is a substance that cannot be broken down to other substances. An element’s properties depend on the structure of its atoms. An atom is the smallest unit of matter that still retains the properties of an element. The formation and function of molecules depend on chemical bonding between atoms. There are four common chemical bonding between atoms, covalent bonds, ionic bonds, hydrogen bonds and van der Waals interactions. Chemical reactions make and break chemical bonds. In a chemical reaction, we have reactants and products.
From this diagram, we can see that one methane molecule and two oxygen molecules are the reactants. One carbon dioxide molecule and two water molecules are the products. In a chemical reaction, we use an arrow to indicate the conversion of the starting materials.
Key terms
Compound: is a substance consisting of two or more different elements combined in a fixed ratio
Neutron: a subatomic particle having no electrical charge, found in the nucleus of an atom.
Protons: a subatomic particle with a single positive electrical charge.
Electrons: a subatomic particle with a single negative electrical charge, one or more electrons move around the nucleus of an atom.
Dalton: a measure of mass for atoms and subatomic particles.
Atomic number: all atoms of a particular element have the same number of protons in their nuclei, the number of protons, which is unique to that element, is called the atomic number.
Mass number: is the sum of protons plus neutrons in the nucleus of an atom.
Radioactive isotopes: is one in which the nucleus decays spontaneously, giving off particles and energy.
Covalent bond: a covalent bond is sharing of a pair of valence electrons by two atoms.
Ionic bond: a chemical bond resulting from the attraction between oppositely charged ions.
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