CHEM 101 Lecture Notes - Lecture 1: Atomic Number, Chemical Formula, Mass Number
Element- The simplest form of matter and in its pure state contains only one type of atom. They
are classified according to their chemical properties.
Symbols of elements
-They are organized in the periodic table
- Elements are represented by chemical symbols
-Most symbols begin with the first letter, first two letter, or first and third letter.
-Rule: Only first letter in the Elements symbol is capitalized
Finding elements
-8 horizontal rows
-18 vertical columns
-main group elements are the first two columns and the last six of the periodic table labeled I
through VIII. Called representative elements
Compound- is represented by combining two or more elemental symbols together. The
chemical formula shows the elements the compound contains and the number of atoms of each
element.
Ex: NaCl one Sodium One Chlorine
Atomic number and the periodic table
The number of the element is called the atomic number. The atomic number tells us the identity
of the element. The periodic table organizes elements by their atomic number.
A look inside the atom
-Subatomic particles are found inside the atom
-chemists are concerned with three subatomic particles
-Protons positively charged
- Neutrons neutral
-electrons negatively charged
Protons
-are positively charged
-positive+negative=neutral
-protons and electrons make up the atoms
Neutrons
-electrically neutral
-same mass as a proton
-This explains why the atomic mass is much heavier than the mass of protons+electrons
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Document Summary
Element- the simplest form of matter and in its pure state contains only one type of atom. They are classified according to their chemical properties. Most symbols begin with the first letter, first two letter, or first and third letter. Rule: only first letter in the elements symbol is capitalized. Main group elements are the first two columns and the last six of the periodic table labeled i through viii. Compound- is represented by combining two or more elemental symbols together. The chemical formula shows the elements the compound contains and the number of atoms of each element. The number of the element is called the atomic number. The atomic number tells us the identity of the element. The periodic table organizes elements by their atomic number. This explains why the atomic mass is much heavier than the mass of protons+electrons. The nucleus is dense, it contains most of the mass of the atom.