Unit 9 – Classification of Matter and Periodic Trends Matter and change of matter is classified by form and available evidence The Periodic Table's function as a technological model is to illustrate repeating patterns among elements and provide structure and information at the heart of modern chemistry

What is Matter? mass Matter is anything that has ___________ and takes up ___________. What are some examples of matter? ____________________________________________________________________ Is light matter? _______________ Is wood matter? _______________ Is air matter? ______________ space No Yes Yes

Classifying Matter All matter can be classified into one of several groups based on the properties of the substances. __________________ are substances that are made up of only one type of particle. Pure substances have a _______ composition _______________ and _________________ are pure substances Pure Substances fixed Elements compounds

Classifying Matter – Elements Elements cannot be broken down into simpler substances through __________ or _______________ processes. Elements are made of atoms. ________ are the smallest particles that still have the properties of that element. Atoms join together to form ____________. chemical physical Atoms compounds

Classifying Matter – Compounds __________________ can be broken into the atoms that make them up through chemical processes. Compounds are unique and different from the _____________ they contain. Water is a compound made of _____________ and _____________. The smallest unit of a compound is called a ________________. elements hydrogen oxygen molecule ?

Classifying Matter – Mixtures Mixtures vs. pure substances A _________________ is matter that has a fixed composition and cannot be broken down or separated by a physical change. A ________________ is a combination of two or more pure substances that can be separated by a physical change. pure substance mixture

Classifying Matter – Mixtures Mixtures are classified by how well they mix ____________________ mixtures are not uniformly mixed and do not look the same throughout. One example is flour mixed with water. The mixture looks like muddy water. ____________________ mixtures look the same throughout. An example would be salt water. Heterogeneous Homogeneous

Classifying Matter – Mixtures ______________ liquids are able to dissolve into each other, and form a homogeneous mixture. __________________ liquids are heterogeneous and form layers of liquid. Gases can also mix with liquids Miscible Immiscible

Classifying Matter – Mixtures Homogeneous Mixtures are known as _______________ There are two types of heterogeneous mixtures Suspensions and Colloids _________________ have large particles that will settle out of the mixture _________________ have particles that are smaller and do not settle out. solutions Suspensions Colloids

Elements Compounds Matter Mixtures Pure Substances Heterogeneous Homogeneous

Physical and Chemical Properties A ______________ property is the way a substance reacts to form new substances with different properties. ___________ is the ability of a substance to combine chemically with other substances. Examples of Chemical Properties _____________________________________________ Reactivity

Physical and Chemical Properties Physical properties are characteristics of a substance that can be observed or measured without changing the ___________________ of the substance. Ex. ________________________________ Ex. _____________________________________ composition

Physical and Chemical Changes A ___________________ change occurs when a substance changes composition by forming one or more new substances. Referred to as chemical reactions Ex. ____________________________________ Chemical changes occur when the atoms are either broken apart from each other or _______________ to form new substances The atoms do not change their ___________ rearranged identities

Physical and Chemical Changes Physical changes do not change the ________________ of the substance. The substance may look different, but it is still made of the same substances. Ex. ____________________________________ _______________ is a physical change. Salt water tastes the same as table salt, because the ________________ of the salt does not change when dissolved. composition Dissolving composition

Periodic chemical properties electron Understood in terms of _____________ ________________ Electrons in outer orbits determine _____________ properties Outer electrons are called ______________ electrons Determines how an atom interacts with other ____________ configuration chemical valence elements

The Periodic Table periods groups Alkali metals Alkaline Earth metals Rows = _____________ (left to right) Columns: families or __________ (up & down) __________________ (Group 1 or IA) ____________________ (Group 2 or IIA) __________________ (Group 17 or VIIA) __________________ (Group 18 or VIIIA) A-group families = main group or ________________ elements ___ -group = transition elements or metals groups Alkali metals Alkaline Earth metals Halogens Noble gases representative B

The periodic table

Metals, nonmetals and semiconductors What makes an element a metal? A substance that has a tendency to lose ____________ to empty its valence shell. What makes an element a nonmetal? A substance that has a tendency to gain ____________ to fill its valence shell. A few elements exhibit properties of both metals and nonmetals. These elements are called ________________ or ___________________ electrons electrons metalloids semi-conductors

Metals, nonmetals and semiconductors stable elements Noble gases - filled shells, _____________ 1A, 2A, & 3A Groups Lose outer electrons to become _______________ ions - ___________ All elements in these groups are ________ 5A, 6A & 7A Groups Tend to ____________ electrons and form negative ions - _____________ All elements in these groups are __________ _________________ - intermediate between metals and nonmetals cations positive metals gain anions nonmetals Semi-conductors

Metals, nonmetals and semiconductors

Periodic Trends Properties of the elements exhibit periodic trends, i.e. these properties repeat themselves as you go across the ____________ of the Periodic Table Known as the __________________ Elements are organized by their __________ properties and give the organization to the Periodic Table periods Periodic Law repeated

Atomic Radius Generally, the atomic radius decreases across a period from left to right and increases down a given group

Relative Atomic Radii

Periodic Trends valence larger attraction smaller Shielding Effect : the ability of the core (inner) electrons to repel the ____________ (outer) electrons. It makes the atom _____________. Nuclear Force of Attraction: this is the electrostatic force of ______________ that exists between protons and electrons. It makes the atom ________. valence larger attraction smaller

Periodic Trends protons Remember, _______________ are increasing one at a time moving from left to right across a period As this happens, the electrons of the outermost shell experience increasingly strong nuclear attraction – electrons become __________ to the nucleus The increased number of protons going across a given period increase the pull of the outer shell electrons – the atom ___________________ Going down a group, each new element represents a new _________ of electrons and thus a larger atom closer becomes smaller shell

Ionization Energy The ionization energy is the energy required to completely remove an ____________ from a gaseous atom The closer an electron is to the ___________, the more difficult it will be to remove - means _________ ionization energy Ionization energies increase moving from left to right across a _____________ (decreasing atomic radius) and decrease moving down a __________ (increasing atomic radius) electron nucleus greater period group

Periodic Trends ionization Metals have lower _______________ energies than non-metals that share their period or group. The easier it is for ___________ to lose their valence electrons the more _______________they will be. Non-metals have higher ionization energies than _________ that share their period or group. This is due to the valence shell being closer to the nucleus, so there is a ___________ nuclear force of attraction. It becomes easier for them to attract and _________ electrons. So the smaller the atom, the easier it is to attract _____________ and the more reactive the non-metal will be. metals reactive metals stronger gain electrons

Ionization Energies

Electronegativity Electronegativity is a measure of the _________________ of an atom for the electrons in a chemical bond - The higher the electronegativity of an atom, the greater its attraction for bonding electrons Elements with low ionization energies have low electronegativities because their nuclei do not exert a strong attractive force on _____________ attraction electrons

Electronegativities of the representative elements

Ionic Radii (Cations) What trends do you observe through studying this chart?

Ionic Radii (Anions) What trends do you observe through studying this chart?

Ionic Radii What similarities did you identify by observing the last two slides? _________________________ _________________________ _________________________ _________________________ _________________________ What differences did you identify by observing the last two slides? _________________________ _________________________ _________________________ _________________________ _________________________

Selected data on the Group 1 Alkali Metals Group 1A Trend Data Selected data on the Group 1 Alkali Metals Chemical symbol, name Atomic number Electron arrangement melting point boiling point Density g/cm3 atomic radius pm Li, lithium 3 2.1 181oC , 454K 1347oC, 1620K 0.53 152 Na, sodium 11 2.8.1 98oC, 371K 883oC, 1156K 0.97 186 K, potassium 19 2.8.8.1 64oC, 337K 774oC, 1047K 0.86 231 Rb, rubidium 37 2.8.18.8.1 39oC, 312K 688oC, 961K 1.48 244 Cs, cesium 55 2.8.18.18.8.1 29oC, 302K 679oC, 952K 1.87 262 Fr, francium 87 2.8.18.32.18.8.1 27oC, 300K 677oC, 950K approx. 2 270  

Valence electrons and ions Outer electrons determine the _______________ properties of an atom Octet rule Atoms attempt to acquire a full valence energy level of ____ electrons, like __________________ The exception is _________, which has only __ electrons This is why atoms form ____________ ________ Electrons can be _____________, _________, or _______________ in the process Example: sodium (Na) chemical 8 the noble gases Helium 2 chemical bonds gained lost shared

Ion Formation and the Periodic Table Elements in a group have the same number of _____________________ The number of ___________________ can be found by looking at the _______________ Group 1 = ___ valence electron Group 2 = ___ valence electrons Group 13 = ___ valence electrons Group 15 = ___ valence electrons Group 16 = ___ valence electrons Group 17 = ___ valence electrons valence electrons valence electrons group number 1 2 3 5 6 7

Ion Formation and the Periodic Table The charge of the ion formed by the elements within a _________ can also be predicted Example: the elements in Group 2 have ____ valence electrons, so they will __________ electrons to get a full valence energy level. Group 1 – lose 1 electron – form _____ ions Group 2 – lose 2 electrons – form _____ ions Group 13 – lose 3 electrons – form ______ ions Group 15 – gain 3 electrons – form ______ ions Group 16 – gain 2 electrons – form ______ ions Group 17 – gain 1 electron – form ______ ions group 2 lose 2 +1 +2 +3 -3 -2 -1

Formation of Ions Na+ Na 11 protons 11 protons 11 electrons

Formation of Ions Cl- Cl 17 protons 17 protons 18 electrons

Electron Dot Diagrams Since we are usually only interested in the behavior of the ___________ electrons, we will occasionally omit the interior electrons from our diagrams. valence Na

Electron Dot Diagrams For atoms with multiple electrons, we follow these guidelines: Imagine that there is a square around the element’s symbol. Place one electron on each side of the square before adding a second electron to any side. O

We will use these diagrams to help us later on when we study chemical bonding. Note that only the main group or representative elements are shown. We do not draw the transition metals using this method.