The bombardier beetle fights the ants that plague it by using chemistry. The natural systems and environment that organisms live in involves chemistry and physics. * Biology is not the only category of science. There is also chemistry, physics, and engineering. * Organization of life is separated into a hierarchy of structural levels. 2. Elements and Compounds * Matter- anything that takes up space and has mass. * Matter also exists in many different forms and has its own characteristics. It is also made up of elements.

Element- a substance that cannot by broken down to other substances by chemical reactions. * Compound- a substance consisting of two or more different elements combined in a fixed ratio. * Compounds have different properties from those of its elements. (Sodium by itself is a metal and chlorine is a poisonous gas. However, combined they made table salt. ) 3. Essential Elements of Life * About 25 of the 92 natural elements are essential to life. Carbon, oxygen, hydrogen, and nitrogen make up 96% of living matter, while phosphorus, sulfur, calcium, and potassium make up the remaining 4%.

Iodine deficiency caused by the lack of iodine causes the thyroid gland to grow to abnormal size. This medical condition is called goiters. * Trace elements- those required by an organism in only small quantities. Ex: Iron and Iodine 4. Subatomic particles * Atom- smallest unit of matter that still retains the properties of an element. * Three types of subatomic particles: neutrons, protons, and electrons. * Electrons travel nearly at the speed of light, forming a cloud around the nucleus. * Dalton is a measurement used to measure subatomic particles. (same as atomic mass unit r AMA) * Neutrons and protons weight about 1 Dalton. Electrons weight so less that they do not contribute in the total mass of an atom 5. Atomic number and atomic mass * Atomic number- number of protons in an element. * Mass number- sum of protons and neutrons. * Atomic mass- the total average mass of an atom. * Atomic mass is concentrated mostly in the nucleus. 6. Isotopes * Isotopes- atoms of the same element that have different numbers of neutrons. * If an isotope is unstable, they have the tendency to lose particles. They become radioactive. * Radioactive isotope- one in which the nucleus decays bounteously, giving off particles and energy.

Eventually, the nucleus decays to an extent where it loses enough protons to form a different element. * Radioactive isotopes are setup as tracers to tallow the process tot metabolism, imp rattan diagnostic tools in medicine, and in sophisticated imaging instruments. 7. The energy levels of electrons * Atoms are mostly empty space. * Only electrons are directly involved in chemical reactions. * An atom’s electrons vary in the amount of energy they possess. * Energy- capacity to cause change * Potential energy- the energy that matter possesses because of its location or Truckee. Matter usually moves to the state of the lowest potential energy. Energy levels(shells)- different states of potential energy that electrons have in an atom * Electrons can change energy levels but only by the loss or gain of energy. * Energy is lost in the form of heat 8. Electron configurations and chemical properties * Electron configuration- the distribution of electrons in the atom’s electron shells. * First Shell- can hold 2 electrons maximum * Second shell- can hold 8 electrons maximum * Valence electrons- electrons that are in the outermost electron shell. Valence hell) * An atom is enervative if it has a completed valence shell. 9. Electron orbital’s * Orbital- the most common AD-space in which an electron spends its time. * First electron shell- one spherical “s” orbital * Second electron shell- 4 orbital’s; one large “S” orbital and three “p” orbital’s (as and up) 10. Covalent Bonds * Chemical bonds- covalent or ionic bonds * Covalent bonds- sharing of a pair of valence electrons by two atoms. Molecule- two or more atoms held together by a covalent bond. * Single bond- one pair of shared electrons * Structural formula- formula that represents both atoms and bonding

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Molecular formula- formula that indicates the different types of atoms in a molecule * Double bond- two pairs of shared valence electrons * Electronegative- the attraction of a particular kind of atom for the electrons of a covalent bond * Monopole covalent bond- electrons shared equally * Polar covalent bond- electrons shared unequally * Water: has a partial negative charge on the oxygen and a partial positive charge on the two hydrogen’s. 11. Ionic bonds * Cationic- positively charred ion * Anion- negatively charged ion * Ionic bond- the attraction between actions and anions Ionic compounds(salts)- compounds formed by ionic bonds. Salts often form crystals. * A convalescent molecule has a definite size and number of atoms, when an ionic molecule does not. * Some salts must lose or gain electrons to balance the number of actions and anions. * Environment also affects the strength of ionic bonds. 12. Weak chemical bonds * Convalescent bonds are the strongest * Hydrogen bonds and van deer walls interactions are weak bonds. * Hydrogen bonds when a hydrogen etymologically bonded to one electronegative atom is also attracted to another electronegative atom. * Van deer Walls interactions are weak because they only form when atoms and molecules are very close together. Proteins can also form hydrogen bonds, ionic bonds, and other weak bonds. 13. Molecular shape and function * a molecule that consists of two atoms are linear * a molecule that consists of more than two atoms are bent. 14. Chemical reactions make and break chemical bonds * chemical reactions-making and breaking of chemical bonds * reactants- starting materials in an chemical equations * products- end result of the chemical equation * chemical equilibrium- the point at which the reactions offset one another exactly and at the same rate.


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