Atoms, Elements, Compounds 6.1

Atoms Matter- anything that has mass and takes up space Atoms are the building blocks of matter ATOMS ARE NOT THE BUILDING BLOCKS OF LIFE

Atoms The structure of atoms Protons- positively charged particles in the center of an atom Electrons- negatively charged particles located outside of an atom Neutrons-neutral particles located in the center of an atom

Elements Element-pure substance that cannot be broken down in other substances by physical or chemical means. Atoms are specific, individual elements. There are 92 elements arranged on the periodic table of elements.

Elements

Elements Isotopes- atoms of the same element but different number of neutrons. Isotopes of the same atom have the same chemical characteristics. Radioactive isotopes- when the instability of the neutrons in an isotope cause the atom to break down and decay. these can be used for medical purposes such as X-rays and other types of scans.

Elements Ions- an ion is formed when an element gains or loses an electron from outside of the center of the atom. When an atom loses an electron, it will become what? Positive When an atom gains an electron, it will become what? Negative

Compounds Compound- pure substance former when two or more different elements combine. Ex. NaCl (salt) Notice the positive charge of sodium (Na) and negative charge of chlorine (Cl) These opposite charges attract each other and make this compound stable.

Chemical bonds Elements are held together by bonds. Bonds happen when electrons are shared or taken over from another element, holding two or more elements together. There are three major types of bonds Covalent Ionic Hydrogen

Chemical bonds Covalent- this is the strongest type of bond. This occurs when outer one element takes over another element’s outer electrons, and they are physically linked. Ex. H20- water molecules are strongly bound together. Think of this bond as a bond between family, strong and unbreakable.

Chemical bonds Ionic bond- this bond forms between positively and negatively charged ions. This bond is very weak and can be easily dissolved Ex. NaCl- salt has weak bonds, that’s why it dissolves so easily in water. Think of this bond as bas friends, because this kind of bond can dissolve easily.

Chemical bonds Van der waals forces are a type of attraction that is strong enough to be called a bond, but weak enough to be broken apart easily. Hydrogen bonds are a strong type of force but can be easily broken apart. The most important hydrogen bond in the body are the bonds between nitrogenous bases in DNA

Key points for 6.1 Atoms are the building blocks for matter, not the building blocks for life Covalent bonds are strong Ionic and hydrogen bonds are weak Compounds are two or more combined elements