BELL-RINGER QUESTION 1. Look at the periodic table of elements…. How are the elements in the periodic table like the alphabet of letters?

2.1 Section Objectives – page 35 Review elements and bonding (In order to prepare for comparing the structure and function of bio-molecules) Today’s Objective: Can be found in the book: Pg

An atom is the smallest particle of an element that has the characteristics of that element. Section 6.1 Summary – pages Atoms are the basic building blocks of all matter. ATOMS

All nuclei contain positively charged particles called protons (p + ). The center of an atom is called the nucleus. Section 6.1 Summary – pages Most contain particles that have no charge, called neutrons (n 0 ). ATOMS

Section 6.1 Summary – pages In the electron cloud there are extremely small, negatively charged particles called electrons (e - ) There is a region of space that surrounds the nucleus called the electron cloud.

Section 6.1 Summary – pages Electrons exist around the nucleus in regions known as energy levels. The first energy level holds 2 electrons. The second level holds up 8 electrons. The third level can hold up to 18 electrons. To know the number of electrons in an energy level can hold after that, use this formula, 2n² Nucleus 8 protons (p+) 8 neutrons (n 0 ) Oxygen atom ATOMS

Section 6.1 Summary – pages The electrons that are in the outer most energy level for that atom are called valence electrons. ATOMS

PRACTICE MAKING ATOMS

Section 6.1 Summary – pages Everything – whether it is a rock, frog, or flower (abiotic or biotic) – is made of substances called elements. ELEMENTS An element is a pure substance made only of one kind of atom. (it cannot be broken down into a simpler chemical substance) Elements differ in the number of protons –Ex: Carbon has 6 protons : Hydrogen has 1 proton

Section 6.1 Summary – pages ELEMENTS

5 B Atomic Number Atomic Symbol Atomic Mass PERIODIC TABLE Atomic Number: The number of protons in an atom defines what element it is. For example carbon atoms have six protons, hydrogen atoms have one, and oxygen atoms have eight. The number of protons in an atom is referred to as the atomic number of that element. Atomic Symbol: The atomic symbol is one or two letters chosen to represent an element ("H" for "hydrogen," etc.). These symbols are used internationally. Atomic Mass: The atomic mass is the sum of protons and neutrons.

Section 6.1 Summary – pages Of all the naturally occurring elements on Earth, only about 25 are essential to living organisms. Carbon, hydrogen, oxygen, and nitrogen make up more that 96 percent of the mass of a human body. ELEMENTS

Chemical Bonding Atoms can join together during chemical bonding to form compounds –A Compound is a substance made of the joined atoms of two or more different elements –Compounds are represented by a chemical formula that shows the proportions of each element in the compound

Covalent bonds Covalent bonds occur when two or more atoms share electrons (co = together, valence= outer electrons) A compound made with covalent bonds is called a molecule

Hydrogen bonds –Molecules with an uneven distribution of electrical charge like water have poles and have a polar attraction –Hydrogen bonds are a weak chemical attraction between polar molecules Water molecules are attracted to each other by hydrogen bonds

Ionic bonds An ion is an atom that has gained or lost an electron. –Ions have a charge due to the unequal number of protons and electrons The attractive force between two ions of opposite charge is known as an ionic bond.

Section 6.1 Summary – pages Chemical reactions occur when bonds are formed or broken, causing substances to recombine into different substances. CHEMICAL REACTIONS

All of the chemical reactions that occur within an organism are referred to as that organism’s metabolism. Section 6.1 Summary – pages CHEMICAL REACTIONS

Section 6.1 Summary – pages In a chemical reaction, substances that undergo chemical reactions, are called reactants. Substances formed by chemical reactions, are called products. CHEMICAL REACTIONS

In this reaction, what are the reactants and what is the product?

Section 1 Check Question 1 Which of the following is an element? D. water C. sodium chloride B. carbon A. chlorophyll

Section 1 Check The answer is B. An element can't be broken down into simpler chemical substances. Chemical elements combine in different ways to form a variety of substances useful to living things. Answer

Section 1 Check The smallest particle of an element that has the characteristics of that element is a(n) __________. Question 2 D. atom C. nucleus B. electron A. proton

Section 1 Check The answer is D. Atoms are the basic building blocks of all matter and have the same general structure, including a nucleus and electrons. Elements found in both living and nonliving things are made of atoms. Nucleus Electron energy levels An atom has a nucleus and electrons in energy levels. Answer

Section 1 Check Which of the following can contain two types of particles? D. electrons Question 3 B. protons C. neutrons A. nucleus

Section 1 Check The answer is A. The nucleus is the center of the atom and may contain both positively charged particles and particles that have no charge. Nucleus 8 protons (p+) 8 neutrons (n 0 ) Oxygen atom Answer