Atomic structure and chemical bonds

Warm up – Nov 4  What are the subatomic particles, their location in the atom and their charges?

Wednesday, Nov. 4, 2015  Warm up  Turn in homework ch 6 sec 1 and 2  Notes on Atomic structure  Vocab flash cards due Friday, Nov 13 & Quiz  Families of the Periodic Table

Vocab words  Electron cloudcovalent bond  Energy levelmolecule  Electron dot diagramchemical reaction  Chemical bondreactants  Ionproducts  Ionic bondchemical formula  Compoundchemical equation  Endothermicexothermic

Atomic Structure a review  Atoms have 3 parts – protons, neutrons and electrons  Protons and neutrons are in the nucleus  Electrons are in the electron cloud  Most of the space is empty

What is the electron cloud?  The electron cloud is the space around the nucleus where the electrons travel  Electrons do not have predictable orbit but they do have a predictable area.

Electron Arrangement  The arrangement of electrons in the electron cloud is different for every element.  Energy levels are the different areas for electron in an atom. Each level has a different amount of energy.

How many electrons are in an energy level?  Energy levels farther from nucleus can hold more electrons  Energy levels close to the nucleus hold fewer electrons  the farther away from the nucleus the more energy an electron has and the easier it is to remove from its outer level

How many electrons are in an energy level?

Valence Electrons  Valence electrons are located in the outermost region of the electron cloud.  Valence electrons are the ones involved in forming chemical bonds  Atoms with a full valence shell are chemically stable  Group 18 (noble gases) are the most stable atoms. These atoms are less stable in compounds.

Periodic Table and Energy Levels Row = # of energy levels # electrons Increase in each group Atoms with a complete outer energy level or one with 8 electrons it is outer level are stable and do not bond easily.

Element families Noble Gas

Noble Gases  Noble gases have a 8 electrons in their outer energy level (or full) They are very happy!  They are very stable  They do not bond easily.

Halogens  Outer energy level have 7 electrons  If they gain one electron they become stable  Halogens are very Reactive  they will bond easily Least reactive Most reactive

Alkali Metals  Alkali metals have one electron in their outer energy Level  When elements react they Lose this electron  the farther away from the nucleus the outer level the easier it is to release the electron

Families of the Periodic Table  Color and answer questions in this activity

Warm up – Nov 5, 2015  How many electrons do the alkali metals have in their outer energy levels?

Thursday, Nov. 5, 2015  Warm up  Electron Dot Diagram  Notes on Bonding  Homework Chapter 7 Section 1 due Friday

Electron Dot Diagram  Is a representation of the atom’s valence state.  Composed of two parts - chemical symbol and dots surrounding the chemical  These electrons determine how an element can react.  Can help you predict how an atom will achieve a full valence shell.  Will help you to see how atoms can become more stable by either gaining, losing or sharing an electron.

What is a dot diagram?  Has 2 parts  chemical symbol for element  dots surround the chemical symbol  What do dots represent?  valence electrons  What are valence electrons?  electrons in outer energy level

Practice ElementChemical symbol Total # of electrons # of valence electrons Dot diagram Potassium Nitrogen Carbon Beryllium Neon Sulfur

Dot Diagram Activity  Review directions and work on this activity.

Warm up – Nov. 6  How many valence electrons for the following elements have?  Li, C, F, Mg, Ar

How elements bond  Chemical bond is the force that holds two atoms together  elements can bond in 4 different ways – they can lose electrons, gain electrons, pool electrons or share electrons with another element

Ionic bonds – loss & gain  Ion – is an atom that is no longer neutral because it has gained or lost an electron  Na loses an electron it is + charge  Cl gains an electron it is - charge

Ionic bond  An ionic bond is the attraction that holds negative ions and positive ions close together Bonds create a new pure Substance called a compound

Using dot diagram to represent chemical reactivity  Once you have a dot diagram you can predict how an atom will achieve a full valence shell  KCl + ion - ion ionic bond

Sharing electrons  Atoms of nonmetal elements become more stable when they share electrons  Example Group 14 – they have 4 valence electrons – easier to be stable by sharing electrons

Covalent Bonds - sharing  A covalent bond is a chemical bond that forms between nonmetal atoms when they share electrons  covalent bonds are called molecular compounds

Using dot diagram to represent chemical reactivity  Electron dot diagram can also be used to show covalent bonds  Cl Cl

Are electrons shared equally?  Some atoms have a greater attraction for electrons than others do.  This difference in attraction can create a polar bond  A polar bond is a bond in which electrons are shared unevenly.  Example of polar bond is water

Chemical Bonds  A molecule is the neutral particle formed when atoms share electrons  Chemical formula is a set of chemical symbols and numbers that shows which elements are in a compound and how many atoms of each are in it

Using dot diagram to represent chemical reactivity ElementsDot diagram for each element Dot diagram for compound formed Chemical Formula Type of Bond Na and F Br and Br Mg and O