Atom, Elements, Molecule
Matter has mass and takes up space.
Atoms are basic building blocks of matter, and cannot be chemically subdivided by ordinary means.
What is an Atom?
Atoms are composed of three type of particles: protons, neutrons, and electron. Protons and neutrons are responsible for most of the atomic mass e.g in a 150 person 149 lbs, 15 oz are protons and neutrons while only 1 oz. is electrons. The mass of an electron is very small (9.108 X 10-28 grams).
Both the protons and neutrons reside in the nucleus. Protons have a postive (+) charge, neutrons have no charge –they are neutral. Electrons reside in orbitals around the nucleus. They have a negative charge (-).
It is the number of protons that determines the atomic number, e.g., H = 1. The number of protons in an element is constant (e.g., H=1, Ur=92) but neutron number may vary, so mass number (protons + neutrons) may vary.
The same element may contain varying numbers of neutrons; these forms of an element are called isotopes. The chemical properties of isotopes are the same, although the physical properties of some isotopes may be different. Some isotopes are radioactive-meaning they "radiate" energy as they decay to a more stable form, perhaps another element half-life: time required for half of the atoms of an element to decay into stable form. Another example is oxygen, with atomic number of 8 can have 8, 9, or 10 neutrons.
What is an ion?
An ion is an electrically charged particle obtained from an atom or chemically bonded group of atoms by adding or removing electrons.
Now what this means is that an ion is the result of taking away, or adding, electrons to an atom or a chemically bonded group of atoms. By taking away, or adding, these electrons, the particle takes on an electrical charge.
Atoms are electrically neutral as they contain an equal number of positive and negative charges.
An atom that adds an extra electron to it becomes a negatively charged ion. This type of ion is called an anion. An atom which loses one or more of its electrons now has a positive charge, and is called a cation.
What is a Molecule?
Molecules are small particles that make up all living and non-living things. They are made up of even tinier particles called atoms. Molecules in living things are made from only about 25 of more than 100 known atoms in the universe. Molecules are made from as few as two atoms to hundreds of millions of atoms.
What are elements?
All matter is made up of elements which are fundamental substances which cannot be broken down by chemical means.
There are 92 elements that occur naturally. The elements hydrogen, carbon, nitrogen and oxygen are the elements that make up most living organisms. Some other elements found in living organisms are: magnesium, calcium, phosphorus, sodium, potassium.
By the late 1800′s many elements had already been discovered. The scientist Dmitri Mendeleev, a Russian chemist, proposed an arrangement of know elements based on their atomic mass. The modern arrangement of the elements is known as the Periodic Table of Elements and is arranged according to the atomic number of elements.
What is a Compound?
A compound is a substance of more than one element, chemically combined. A more scientific definition is that a compound is a type of matter composed of atoms of two or more elements chemically combined in fixed proportions.
An example of a compound would be water. It is a compound that contains the elements hydrogen and oxygen fixed in the ratio 2 to 1. A compound has new properties unlike the elements which make it up. A compound has a chemical formula such as H2O.
What is a mixture?
A mixture is a material that can be separated by physical means into two or more substances. A classic example of a mixture lab would be one in which you were presented a mixture of sand, iron filings, and salt.
Category: Chemistry
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The elements have been given a shorthand way of writing it, by using symbols. Symbols were invented by Jons Jakob Berzelius