Chapter 3-1: Chemistry of Life
Warmup: What are the three main subatomic particles of the atom? What are there charges?
Objectives:
To learn chemistry vocabulary.
To define the structure of atoms.
Understand electron organization
Matter
Matter occupies space and has mass.
Every living and non-living thing is made of matter.
It can exist as a solid, liquid, or gas.
Elements
Elements are substances made up of only one kind of atom.
The smallest particles of an element that have the characteristics of that element are atoms.
The following elements make up 96% of the body weight of organisms: Oxygen, Carbon, Hydrogen, Nitrogen.
Substances that are composed of two or more different elements are called compounds.
For example, water is a compound because it is composed of hydrogen and oxygen.
Atoms
An atom is composed of subatomic particles.
Protons – positive charged particle in nucleus
Neutrons – neutral particles in nucleus
Electrons – negatively charged particles surrounding nucleus in a cloud
Atoms are neutral because the number of protons equals the number of electrons
An atom has a positive core surrounded by a negative region. Negative and positive charged particles are attracted to each other like magnets.
Atomic Number
The atomic number is the number of protons.
All atoms of an element have the same atomic number and number of protons.
The number of protons contributes to the physical properties of an element.
Atoms are neutral, therefore the number of electrons is equal to the number of protons.
Isotopes
Isotopes are atoms that have the same number of protons and differ only in the number of neutrons.
Most isotopes are stable but radioactive isotopes are unstable and break down releasing radiation.
Radiation can be detected, so radioactive isotopes are useful as labels in scientific research and medical diagnostictests.
Atomic Mass
The atomic mass is calculated as the sum of the mass of protons, electrons, and neutrons.
The mass of electrons is very small and doesnot contribute much to the atomic mass.
The atomic mass is the average number of protons and neutrons.
Each proton and each neutron is 1 atomic mass unit.
Periodic Table
The periodic table is a table showing the atomic symbol, atomic mass, and atomic number of all of the elements.
The elements are arranged from left to right according to their atomic number.
Vertical columns are called families. Families have the same number of valence electrons
Horizontal rows are called periods and periods have the same number of electron shells.
Atomic Symbols
In the periodic table, each element is contained in a box with important information
Atomic symbol or abbreviation for each element
Atomic number and Atomic mass
Electrons
Electrons are arranged in shells around the nucleus
Some models draw the shells as orbitals or circles
The innermost shell holds two electrons
Outer shells hold eight electrons
Electrons fill the inner shell(s) first
Bohr models can be used to draw atoms to show electrons in the shells
Electrons in the outermost shell are valence electrons
Model for Atoms
Valence Electrons
The outer shell is called the valence shell.
Atoms with incomplete outer shells are reactive with other atoms in a way that allows it to complete the outer shell.
Atoms react to give up, receive, or share electrons to produce a completed outer shell.
Atoms with a complete outer shell do not react with other atoms.
Chemical bonds form when two or more atoms react to fill their outer shells with electrons.
Lewis Models
Valence electrons can be modeled using a Lewis structure
Lewis structure is element symbol surrounded by dots to represent valence electrons
Activity for Periodic Table and Valence Electrons
Use the periodic table to complete the first part of the worksheet.
Determine the # of sub atomic particles
With your partner use colored chips to model the indicated atoms
Remember –
Protons and neutrons in the nucleus
Electrons in shells
2 electrons in inner first shell
8 electrons in outer shells
Write down the number of valence electrons from your model
Record the valence electrons using a Lewis structure (element symbol surrounded by dots) on your worksheet
Pay attention to patterns in number of shells and number of electrons in valence shell