Chapter 17 - Atomic Structure

Scientists have developed their own shorthand for dealing with long, complicated names. Chemical symbols consist of one capital letter or a capital letter plus one or two smaller letters. Scientific Shorthand

Capitals matter! Element symbols contain ONE capital letter followed by lowercase letter(s) if necessary. Scientists use two letters for some elements because there are more elements than letters. Metals that form Bright blue Co vs. CO Poisonous Gas Solid compounds Chemical Symbols

An element is matter that is composed of one type of atom, which is the smallest piece of matter that still retains the property of the element. Atoms are composed of particles called protons, neutrons, and electrons HOW DO WE KNOW THIS? Atomic Components

Studying Atoms 1. Ancient Greek Models of Atoms –400 BC –Greek Philosopher Democritus- named atoms(atomos) –Believed that all matter consisted of small particles that could not be divided and were impossible to destroy. –He called these particles atoms.

2. Dalton’s Atomic Theory – still use parts of this –John Dalton – 1803 All elements are composed of atoms Atoms of the same element are alike, atoms of different elements are different Compounds are formed by joining two or more of these elements in a set ratio Atoms of the same elementAtoms of different elements

3. Plum Pudding Model –JJ Thomson – Plum Pudding Most of the atom was positively charged Atoms had negative charges embedded in pos. charged material

4. Rutherford’s Model –Ernest Rutherford – gold foil experiment - nucleus Gold Foil Experiment – Rutherford fired positively charged particles at a sheet of gold foil. Most passed through.(like charges repel) Rutherford discovered the nucleus as a result of his experiment

5. Bohr Model –Neils Bohr – 1913 Worked with Rutherford Electrons move in definite orbits “Orbits” are referred to as energy levels

Modern Atomic Theory Energy levels – the possible energies that electrons can have Electrons cannot exist between energy levels Electrons can move from one energy level to another. gains –when an atom gains (moves up) loses – loses energy (falls to a lower level)

Electrons Losing Energy When an electron loses energy, it emits light. Each element has a specific wavelength and frequency at which the light is emitted. This gives each element a unique color. –Example: Copper Chloride– Sodium Chloride– Potassium Chloride– We can see this through flame testsflame tests

6. Electron Cloud Model – current Atomic Model Electron cloud is a visual model of the most likely locations and motions of electrons in atoms. The electron cloud is a visual model of the probable locations of electrons in an atom. The probability of finding an electron is higher in the denser regions of the cloud.

The Structure of the Atom Atoms consist of subatomic particles –Protons Positive charge Located in the nucleus –Neutrons No charge Located in the nucleus –Electrons Negative charge Located in the electron cloud

Subatomic Particles

Protons and neutrons are made up of smaller particles called quarks. So far, scientists have confirmed the existence of six uniquely different quarks Quarks—Even Smaller Particles

Scientists theorize that an arrangement of three quarks held together with the strong nuclear force produces a proton. A different arrangement of three quarks produces a neutron 1. up5. top 2. down6. bottom 3. charm 4. strange Quarks He

To study quarks, scientists accelerate charge particles to tremendous speeds and then force them to collide with—or smash into—protons. This collision causes the proton to break apart. The particles that result from the collision can be detected by various collection devises. Atom smashers Finding Quarks

Atomic Number and Mass Number Atomic Number – Identifies the element –# of protons in the nucleus of an atom –Different elements have different numbers of protons –When this number changes, you get a different element. Mass Number –Sum of an atoms protons and neutrons –Number of neutrons = mass # - Atomic #

Isotopes Isotopes are atoms of the same element with different numbers of neutrons and different mass numbers. This can also be written in Hyphen Notation  Carbon - 12 Nuclear Notation 

Average Atomic Mass The atomic mass that is on the periodic table, is a weighted average of all of the isotopes of a given element. The more abundant an isotope is, the more heavily it counts towards the average atomic mass. Example: Calculate the average atomic Mass. Mass numberAbundance Si % Si % Si %

Atomic Orbitals Orbital is a region of space around the nucleus where an electron is likely to be found.

Electron Configurations Ground state – when all the electrons in an atom are in orbitals with the lowest possible energies.