The Chemical basis of Life CHAPTER 2 The Chemical basis of Life

Matter Anything that occupies ___________ and has _________. Mass is measured by how much something weighs Can exist as: ____________

Element- The simplest form of matter that cannot be broken into smaller substances by natural means. Hydrogen, Oxygen, Carbon, and Nitrogen make up 96% of the matter in an animal’s body. Elements are referred to by a ____________ ______________and are organized in the Periodic Table of Elements. What is an element?

GROUP PERIOD 

Elements in an Animal’s Body Major Elements Oxygen (O) Carbon (C) Hydrogen (H) Nitrogen (N) Minor Elements Calcium (Ca) Phosphorus (P) Potassium (K) Sulfur (S) Sodium (Na) Chlorine (Cl) Magnesium (Mg)

Trace Elements Silicone (Si) Aluminum (Al) Iron (Fe)* Manganese (Mn) Fluorine (F) Vanadium (V) Chromium (Cr) Copper (Cu)* Boron (B) Cobalt (Co) Zinc (Zn)* Selenium (Se) Molybdenum (Mo) Tin (Sn) Iodine (I)*

Atoms The ___________ __________ of an element that retains the unique properties of that element. Composed of 3 subatomic particles: _________________

Protons and Neutrons are found in the __________________. Protons have a ______________charge. Neutrons have __________ charge and are considered neutral. Each proton and each neutron has an atomic mass of ~1. Together protons and neutrons determine the atomic _______________ of the atom. The atomic ______________ of an element is equal to the number of protons in that element. Protons & Neutrons

Tiny particles that remain in constant motion around the ________________. So tiny that their mass does not contribute to the atomic weight of the atom. Electrons have a ____________charge. The overall charge of an atom is neutral because an atom has equal numbers of protons, neutrons, and electrons*. Electrons

Atomic Number

Atoms continued The atomic number of an atom tells us how many ______________ it has. This number cannot change as it is what makes each element unique. If an atom loses or gains an ______________, it becomes positively or negatively charged, thereby becoming an __________. If an atom has equal numbers of protons and electrons, but a different amount of neutrons, it is called an ________________ of the element.

Isotopes Ions Na atom Na+ ion 10electrons, 11protons 11electrons,

Electron Shells Shells are pathways around the nucleus where electrons orbit There are one or more shells surrounding the nucleus, depending on the # of electrons. Only a certain number of electrons can be on each pathway/shell. Electrons first fill the innermost shell before moving to the next shell.

Electron Shells First shell can contain two electrons. Second shell can contain eight electrons. If the outermost shell is not full, then an atom will be more active in an attempt to fill it. Electron Shells

Electron Shells Atoms are stable when their outermost shells are full. Atoms with incomplete shells are constantly trying to find complete their outer shell. The outermost shells of Helium and Neon are full, so they are considered chemically inactive/inert. Electron Shells

Molecules and Compounds ___________________- form when two or more atoms are joined together by chemical bonds. Molecule of the __________________-two or more atoms of the same element are joined together. Example: Oxygen, O2 ___________________ -two or more atoms from different elements are joined together. NaCl, CO2

Chemical Bonds Chemical bonding means that atoms are _________________ or __________________ electrons. By doing this, each atom can be sure that its outermost shell is full. Atoms are constantly trying to become more stable. Types of chemical bonds: _________________, _________________, _________________

Covalent Bonds Bonds formed when atoms ______________ electrons. Classification depends on how many electrons are shared. single covalent bond: ______ electron is shared double covalent bond: ______ electrons are shared triple covalent bond: ______ electrons are shared The shared electrons spend part of their time in the outermost shell of each of the atoms.

Covalent Bonds

Polar Water Molecule In some covalently bonded molecules, shared electrons may spend more time near one atom than the other Shared electrons in a water molecule spend more time near the __________atom than __________ atoms Poles are created Gives molecule a slight _________ charge on H side of molecule and slight _________charge on O side of molecule 21

Formed when electrons are _________________ from one atom to another From an atom with one or two electrons in the outer shell to an atom that needs one or two electrons to fill its outer shell Transfer causes a ______ charge on the atom that gave up the electron and a ______ charge on the atom that receives the electron. Since opposites attract, the two atoms “stick” together through electrostatic attraction. Ionic Bonds

Types of Ions _______________Ions with a net positive charge after electron transfer. Ca+, K+, Na+ _______________Ions with a net negative charge after electron transfer. Cl-, F- Ions are important in contraction of muscle fibers, transmission of nerve impulses, and maintenance of water balance.

__________ __________ bond between hydrogen atoms already ______________ bonded in a molecule to oppositely ______________ particles. (F,N,O) Hydrogen bonding can alter the shape of large molecules, which can be seen in the many twists and turns of some proteins and the DNA helix. Hydrogen Bonds

Chemical Reactions The formation and breaking of chemical bonds. Require energy input or release of energy. Chemical Equation- reaction is described in written form. X + Y → Z (reactants) (products) Arrow indicates direction of the reaction

Types of Chemical Reactions 1. ____________________ Reaction- new and more complex molecule is made from multiple, simpler chemicals. X + Y -> XY O + O -> O2 2. ___________________ Reaction- single complex chemical is broken down into multiple, simpler chemicals. XY -> X + Y MgCl2 -> Mg + Cl2 3. __________________ Reaction- certain atoms are exchanged between molecules. Combination of synthesis and decomposition reaction. WX + YZ -> WZ + YX NaCl + AgNO3 -> NaNO3 + AgCl +