Chemistry

Chemistry Vocabulary Element: Elements are chemically the simplest substances and hence cannot be broken down further using chemical methods. Elements can only be changed into other elements using nuclear methods. Atom: An atom is the defining structure of an element, which cannot be broken by any chemical means.

A chemical reaction: A reaction or chemical reaction is a chemical change which forms new substances. Ex: OH + H H 2 O (reactant) (product) Compound: A substance formed by the reaction of two or more chemical elements. Molecule: a molecule refers to two or more atoms which have chemically combined to form a single species.

Atomic Structure

The structure of the atom ELECTRON – negative, mass nearly nothing PROTON – positive, same mass as neutron (“1”) NEUTRON – neutral, same mass as proton (“1”) The Ancient Greeks used to believe that everything was made up of very small particles. I did some experiments in 1808 that proved this and called these particles ATOMS: Dalton

The Atom Nucleus Electron Shell or Orbit

The Atom Hydrogen Proton Electron Hydrogen has one proton, one electron and NO neutrons

Mass and atomic number ParticleRelative MassRelative Charge Proton11 Neutron10 Electron0 MASS NUMBER = number of protons + number of neutrons SYMBOL PROTON NUMBER = number of protons (obviously)

The Atom Carbon Protons Neutrons Electrons Carbon has six electrons, six protons and six neutrons.

The Atom Oxygen Protons Neutrons Electrons Oxygen has eight electrons, eight protons and eight neutrons.

The Atom Sodium Protons Neutrons Electrons Sodium has eleven electrons, eleven protons and twelve neutrons.

How many protons, neutrons and electrons?

Mendeleev Periodic table The periodic table arranges all the elements in groups according to their properties. Horizontal rows are called PERIODS Vertical columns are called GROUPS

HHe LiBeBCNOFNe Na MgMg AlSiPSClAr KCaFeNi CuCu ZnBrKr AgIXe Pt AuAu HgHg The Periodic Table Fact 1: Elements in the same group have the same number of electrons in the outer shell (this correspond to their group number) E.g. all group 1 metals have __ electron in their outer shell These elements have __ electrons in their outer shell These elements have __ electrons in their outer shells

HHe LiBeBCNOFNe Na MgMg AlSiPSClAr KCaFeNi CuCu ZnBrKr AgIXe Pt AuAu HgHg The Periodic Table Fact 2: As you move down through the periods an extra electron shell is added: E.g. Lithium has 3 electron in the configuration 2,1 Potassium has 19 electrons in the configuration __,__,__ Sodium has 11 electrons in the configuration 2,8,1

HHe LiBeBCNOFNe Na MgMg AlSiPSClAr KCaFeNi CuCu ZnBrKr AgIXe Pt AuAu HgHg The Periodic Table Fact 3: Most of the elements are metals: These elements are metals This line divides metals from non- metals These elements are non-metals

HHe LiBeBCNOFNe Na MgMg AlSiPSClAr KCaFeNi CuCu ZnBrKr AgIXe Pt AuAu HgHg The Periodic Table Fact 4: (Most important) All of the elements in the same group have similar PROPERTIES. This is how I thought of the periodic table in the first place. This is called PERIODICITY. E.g. consider the group 1 metals. They all: 1)Are soft 2)Can be easily cut with a knife 3)React with water

How shells fill The first electron shell can only hold a maximum of two electrons. The second electron shell can hold a maximum of eight electrons. The third electron shell can also hold a maximum of eight electrons. The fourth electron shell can also hold eight electrons.

Electron structure Consider an atom of Potassium: Potassium has 19 electrons. These are arranged in shells… Nucleus The inner shell has __ electrons The next shell has __ electrons The next shell has the remaining __ electron Electron structure = 2,8,8,1

Forming Bonds Atoms can bond to each other and make molecules. These bonds are what hold molecules together. Bonds form when atoms either give away or share electrons.

Covalent Bonds Covalent bonds are bonds in which atoms share electrons.

Ionic Bonds Ionic bonds form when one atom takes an electron from another atom. Stable atoms are atoms that have full valence shells. Unstable atoms are atoms that do not have filled valence shells

Water Water is covalently bonded. It is more positive on one side than another. This makes it charged and can pull apart other charged particles.

pH When something is an acid it contains a lot of H +(ions) When something is a base it contains a lot of OH -(ions) When it is neutral it contains the same amount of H ions and Oh ions.

pH Scale