Section 2.1 What three subatomic particles make up atoms? How are all of the isotopes of an element similar? What are the two main types of chemical bonds?

2.1 Vocabulary atom ionic bond nucleus ion electron covalent bond element molecule isotope van der Waals forces compound

Chapter 2 The Chemistry of Life Atom – the building blocks of matter (100 million atoms side by side = 1 cm in length) Subatomic particles in the atom: 1. Protons Inside the _____________ 2. Neutrons 3. Electrons

Protons – positive charge (atomic number) Neutrons – neutral (no charge) Electron – negative charge Protons and neutrons about the same mass Electron is very small (1/1840 mass of proton) Electrons in constant motion around the nucleus

Elements in the human body # Protons = # electrons Overall charge of atom is ________________ Proton # also called the _______________ ____________________.

Elements Pure substance Made of one type of atom More than 100, but only about 25 in living organisms

The Periodic Table of Elements Interactive

Isotopes Atoms of the same element that have a different number of neutrons Identified by their mass number example: C-12 C-13 C-14 All isotopes of an element have the same chemical properties because same number of electrons

Radioactive Isotopes Nuclei are unstable and break down at a constant rate over time Important scientific/practical uses Geologists determine age of rocks and fossils Treat cancer Kill bacteria that cause food to spoil Labels (tracers) to follow movements of substances in organisms

Chemical Compounds Substance formed by the chemical combination of 2 or more elements Combine in definite proportions Use chemical formulas to identify them (H 2 O, NaCl) Physical and chemical properties of a compound are different from the elements making it up

Chemical Bonds Bonding involves the electrons in the atoms Ionic Bond forms when electrons are transferred from one atom to another Cation-an atom that loses electrons, positive charge Anion-an atom that gains electrons, negative charge

Ionic Bond NaCl

Covalent Bond H 2 O

Covalent Bonds Electrons are shared between atoms Single bond ______ electrons shared Double bond ______ electrons shared Triple bond _______ electrons shared Molecule- smallest unit of most compounds -formed when atoms bond covalently

van der Waals forces Intermolecular forces of attraction Molecules get close together and attraction develops between oppositely charged regions of nearby molecules

Gecko Gecko’s foot covered by half a million tiny hairs Comes in contact with a large area of the wall at molecular level