Presentation on theme: "Matter, atoms, and the periodic table"— Presentation transcript:
1Matter, atoms, and the periodic table Matter and moreMatter, atoms, and the periodic table
2In this unit Properties of matter physical/chemical Composition of Matteratoms, elements, compounds and mixturesMeasuring matter (calculating density)Changes of StateAtomic StructureThe Periodic Table
3Describing matterCharacteristics, composition and properties
4What is matter?What do you think of when you hear the term “matter”? matter is anything that has mass and takes up space Is air matter? yes! Are you made of matter? What are some other examples of matter? write down at least 3 examples in your notebook THEN raise your hand to share
5Properties of matterAll matter has two types of properties: Physical Properties Chemical Properties A physical property is a characteristic of a pure substance that can be observed without changing it into another substance (in other words, physical properties can be observed) A chemical property is a characteristic of a pure substance that describes its ability to change into different substances
6Examples of properties physicalchemicalColor Texture Hardness Weight Volume State of matter DensityReactivity Flammability Toxicity Chemical stability pH
7What is matter made of?Matter is made of elements An element is a pure substance that cannot be broken down into any other substance by chemical or physical means For example, gold (Au) is an element, it cannot be broken down into any other substances
8What are elements made of Elements are made of smaller particles called atoms An atom is the basic particle from which all elements are made Atoms can combine through chemical bonds to form molecules or compounds
9moleculeA molecule is a group of two or more atoms held together by chemical bonds
10compoundsA compound is a pure substance made of two of more different elements chemically combined in a set ratio This ratio can be shown in a chemical formula, such as CO2 (pictured on right)**All compounds are molecules but not all molecules are compounds
12The bottom lineWhen elements are chemically combined, they form compounds having properties that are different from those of the uncombined elements. For Example: Table sugar (C12H22O11) is a compound made of the elements carbon, hydrogen, and oxygen. The sugar crystals do not resemble the gases oxygen and hydrogen or the black carbon you see in charcoal.
13Math skills sidebar: ratios A ratio compares two numbers. It tells you how much you have of one item compared to how much you have of another. For example, a cookie recipe calls for 2 cups of flour to every 1 cup of sugar. You can write the ratio of flour to sugar as 2 to 1, or 2 : 1. The chemical formula for rust, a compound made from the elements iron (Fe) and oxygen (O), may be written as Fe2O3. In this compound, the ratio of iron atoms to oxygen atoms is 2 : 3. This compound is different from FeO, a compound in which the ratio of iron atoms to oxygen atoms is 1 : 1. Practice Problem What is the ratio of nitrogen atoms (N) to oxygen atoms (O) in a compound with the formula N2O5? Is it the same as the compound NO2? Explain.
14Mixtures matter!Elements and compounds are pure substances, but most of the materials you see every day are not. Instead, they are mixtures. A mixture is two or more substances— elements, compounds, or both—that are together in the same place but are not chemically combined Each substance in a mixture keeps its individual properties. Also, the parts of a mixture are not combined in a set ratio.
15Types of mixturesHomogenousheterogeneousA mixture in which substances are evenly distributed throughout the mixture. Example: iced teaA mixture in which pure substances are unevenly distributed throughout the mixture. Example: trail mix
18How can we measure matter? Weight- A measure of the force of gravity on an object.Mass- The amount of matter in an object.SI unit=kgVolume- The amount of space an object takes up.Formula: L x W x HCommon units: mL, L, cm3SI Unit= International System of UNits
19densityDensity- The measurement of how much mass of a substance is contained in a given volume.
24TimelineBC: Democritus- first person to proposed that matter was made of tiny particles that could not be broken down1808: Dalton- created the 1st atomic theory; believed atoms to be solid, tiny balls1897: Thomson- discovered electrons, proposed the existence of a (+) particle and proved that atoms were made up of even smaller particles1911: Rutherford- discovered protons; showed that atoms has a nucleus and were mostly empty space1913: Bohr- proposed that electrons moved in “shells” around the nucleus1932: Chadwick- discovered neutrons
251932-current model Protons and neutrons are located in the nucleus Electrons move freely and quickly throughout the electron cloud
26Particles in the atom p+ e- n Particle Symbol Charge Relative mass(amu)Protonp++1Electrone--Neutronn1/836
27Atomic Number and MassOn board: atomic #=# of p atomic mass = p+n # of p = # of e except in ions and isotopes
28Practice problemsIron (Fe) has an atomic mass of and it’s atomic number is 26How many neutrons does an atom of Iron have?How many electrons?How many protons?# of protons = 26 (atomic number)# of neutrons = 56-26= 30 (round atomic mass to nearest whole number)# of electrons = 26Notice that the atomic # = the # of p and the # of e# of n will always be equal to atomic mass-atomic number
29IonsWhat do you think would happen if an atom gained an electron? What if it lost an electron? An ion is an atom or group of atoms that has become electrically charge ions can be positive or negative Examples: Na + OH -
30Atomic behavior – Introduction (read only) The way that atoms behave depends on their atomic structureSome atoms are more likely than others to form bondsAtoms that are considered stable are less likely to form bonds…so how do you know if an atom is stable?Although the current atomic model shows that electrons move about in an electron cloud, we will be using electron shells to show how an atom is organized
31Atoms have energy shells surrounding their nucleus Each shell can hold a certain amount od electronsIf an atom’s outermost shell is full then atom is stable
32Example - stableThis Helium (He) atom is stable because its outermost shell is complete **The 1st energy shell in an atom can only hold 2 electrons
33Example – unstableRecall that the 2nd energy shell can hold 8 electrons Oxygen’s outermost shell is not full, so the atom is unstable
34Energy levels Energy level Letter Number of electrons held 1 s 2 p 8 3 184f32
36Covalent, Ionic, and polar Bonds Atomic BondingCovalent, Ionic, and polar Bonds
37Essential QuestionsWhile you are taking your notes and participation in class discussions keep the following questions in mind: 1. Why isn’t the world made only of elements? 2. How do the atoms of different elements combine to form compounds? 3. How is the number of valence electrons related to the reactivity of an element?
38VideoBrainPop: Chemical Bonds “Atomic Glue!!” eml Question: What are the two main types of chemical bonds? Answer: Ionic and CovalentBefore beginning the video, tell students to pay close attention and listen for the two main types of bonds
39Valence electronsThe number of valence electrons in an atom of an element determines: properties of that element the ways in which the atom can bond with other atoms
40Skydivers on the outer edges of the circle are less likely to be held together with the group
41Lewis Dot ModelsRemember that we can show the number of valence electrons an atom has by drawing a Lewis Dot Diagram
42Stability and BondingMost atoms are more stable and less likely to react when they have eight valence electrons For example ,the following atoms all have eight valence electrons and are very unreactive neon argon krypton xenon
43The goal of bondingWhen atoms react, they usually do so in a way that makes each atom more stable. One of two things can happen: the number of valence electrons increases to eight (or two, in the case of hydrogen) the atom gives up its most loosely held valence electrons Once atoms have done this, they are chemically bonded chemical bond- The force that holds atoms together *when atoms bond, a chemical reaction will occur (we will learn more about this later in the unit)
45Patterns in the periodic table READ TO CLASS: As the number of protons (atomic number) increases, the number of electrons also increases. As a result, the properties of the elements change in a regular way across a period. Figure 11 compares the electron dot diagrams of some of the elements from left to right across the table. Notice that each element has one more valence electron than the element to its left.
46remember**The group number indicates the number of valence electrons that an atom has*For example:elements in Group 2 have two valence electronselements in Group 17 have seven valence electrons*The elements within a group have similar properties because they all have the same number of valence electrons in their atoms*Atoms in the same group or family will also behave the same way
47Interpreting the periodic table Look at the elements in the column just to the left of the noble gases – Group 17 The elements in Group 17 are called the halogens Question: How many electrons will the elements in this group have? Answer: 7 A gain of just one more electron gives these atoms the stable number of eight electrons In contrast, the elements in group 1 known as alkali metals only have one valence electron so giving one away will make the atom stable