Chapter 2, Section 2 Combinations of Atoms

Interactions of Atoms Compounds Atoms of more than one type of element that have been chemically bonded together Often have different properties than the elements that formed them

Interactions of Atoms Chemical Formulas Show the ratios and types of atoms in a compound NaCl H20 HCl

Interactions of Atoms Chemical Properties Describe changes that occur when one substance reacts with another substance

Bonding Chemical Bond Force that holds atoms together in a compound Form when atoms share or exchange electrons in their outermost energy level Outer energy level is considered stable (and won’t form bonds) when it has 8 electrons Chemical Bond

Bonding Covalent Bonds Form when atoms share the electrons in their outermost energy levels

Bonding Molecule Group of atoms connected by covalent bonds

Bonding Ionic Bonds Form when oppositely charged ions join together to form a neutral compound

Bonding Metallic Bonds Occur in metals Electrons are free to move from one positively charged ion to another Results in conductivity

Bonding Polar Molecules Molecules with slight positive and negative charges due to unequal sharing of electrons Example: Water

Bonding Hydrogen Bonds Weak bonds formed between the negative end of one water molecule and the positive end of another water molecule

Mixtures Mixture Two or more substances that are not chemically combined

Mixtures Heterogeneous Mixtures Not mixed evenly Each component retains its own properties

Mixtures Homogeneous Mixtures Evenly mixed Properties of the components are often different from the properties of the mixture Often called a solution

Separating Mixtures and Compounds Mixtures vs. Compounds Mixtures can be separated by physical means Compounds must be separated by chemical means