Chapter 2 Chemistry of Life Section 1 Composition of Matter pg. 31

Is air matter? Does it occupy space? Does it have mass? Matter- anything that occupies space and has mass Is air matter? Does it occupy space? Does it have mass?

Mass- the quantity of matter an object has; mass doesn’t change Weight- the force of gravity acting on mass

Elements and Atoms oxygen, carbon, hydrogen, and nitrogen Elements- substances that cannot be broken down chemically into simpler kinds of matter > 100 have been identified 90% of living things are composed of just 4 elements: oxygen, carbon, hydrogen, and nitrogen

The Periodic Table A chart showing information about the elements (the back cover of most of your books) Dmitri Mendeleev

C 6 Carbon 12.0107 Element symbol Element name Atomic number = # of protons Element symbol Element name Atomic mass (Round this to get mass number) How can you determine the number of electrons?

The number of protons is the ATOMIC NUMBER How do you find the number of each type of particle? (protons, neutrons, and electrons) The number of protons is the ATOMIC NUMBER Elements are arranged on the Periodic Table by their atomic number The number of electrons is the same as the number of protons The MASS NUMBER is the atomic mass rounded.

The number of neutrons is calculated by subtracting the atomic number from the mass number.

Many symbols of elements are based on their Latin names Lead Pb Plumbum Sodium Na Natrium

What is an atom? Atom-the simplest particle of an element that retains all of the properties of that element The world’s largest gold bar: 551 lbs The price of gold is over $900.00/oz 551 lbs x 16 oz/lb = 8,816 oz = $$$$$

The Structure of the Atom There are many models used to represent the structure of an atom. One of those is the Bohr model: It shows the nucleus or the center of the atom where the protons and neutrons are located. It also shows the arrangement of electrons in energy levels around the nucleus.

3 particles of an atom Protons- in the nucleus; positive charge Electrons- in energy levels around the nucleus ; negative charge Neutrons- in the nucleus; neutral charge The mass number is the number of protons + the number of neutrons

Other atom models: Notice the protons and neutrons in the nucleus… and the electrons spinning around the nucleus…

Energy Levels of Atoms 1st energy level holds 2e- Energy levels are also called orbitals. Each energy level can hold only a certain # of electrons… 1st energy level holds 2e- 2nd energy level holds 8e- 3rd energy level holds 8e- 4th energy level holds 16e- What element is shown above?

Isotopes Atoms of the same element that have different numbers of neutrons. *Red= proton Gray=neutron Hydrogen Deuterium Tritium Protons 1 1 1 Electrons 1 1 1 Neutrons 0 1 2

Compounds Compound- substances made up of two or more elements in fixed proportions. Represented by a chemical formula. For example, water: H2O and glucose: C6H12O6