Topic 1 The Atom

Topic 1-Outline Parts of the Atom a. Proton b. Neutron c. Electron d. Rutherford’s Gold Foil Experiment 2. The Structure of the Atom a. Mass number b. Number of protons c. Number of neutrons d. Number of electrons e. Atomic number f. Ions Isotopes Atomic Mass -be able to calculate Electron Configuration a. Know the diagonal rule b. Three methods c. Ground state vs. excited state 6. Types of Matter a. Homogeneous vs. heterogeneous matter b. Pure Substances c. Mixtures d. Distinguishing between mixtures and compounds i. Filtering ii. Chromatography iii. Distillation

Definitions/Terms to Know 1. Proton A positively charged subatomic particle found in the nucleus of an atom. It has a mass of 1 amu and a positive charge

2. Neutron A subatomic particle with no (neutral) charge and a mass of 1 amu; found in the nucleus of an atom

Protons + neutrons in the nucleus 3. Nucleons Protons + neutrons in the nucleus of an atom

4. Electron orbiting around the nucleus. A negatively charged subatomic particle found orbiting around the nucleus. It has no mass and a negative charge In the modern theory,(aka the wave-mechanical model) the electron has both properties of a wave and particle. This is referred to as the wave-particle duality of the electron

Models of the Atom 1. Dalton (1803)-pictured atoms as tiny, indestructible particles, with no internal structure. Thomson (1897)-electrons embedded in a sphere of positive electrical charge Plum pudding model

Electrons move around the nucleus. Atom is mostly empty space. Rutherford (1922)-finds that an atom has a small, dense, positively charged nucleus. Electrons move around the nucleus. Atom is mostly empty space. Never mentions neutrons.

Rutherford’s Gold Foil Experiment An atom is mostly empty space. It consists of a positively charged, dense center (nucleus) with electrons found orbiting the nucleus. He never mentioned neutrons.

4. Bohr (1913)-the electrons move in circular orbits at fixed distances from the nucleus

5. Schrodinger (1926)-describes the motion of electrons in atoms. His work leads to the electron cloud model. Orbital-region of space in which there is a high probability of finding an electron

The Atom

Mass Number Number of Protons Equal to the # protons + # neutrons Must be a whole number Equal to the atomic mass rounded to the nearest whole number Number of Protons Equal to the atomic number Is also the nuclear charge

How to find the number of protons, electrons, neutrons, atomic number, mass number # protons = atomic number (look on Periodic Table) # neutrons = mass number - # protons mass number = # protons + # neutrons or atomic mass rounded to nearest whole number (depending on the information given) # electrons = # protons (if neutral) Atomic mass = look on Periodic Table The weighted average of the masses of the naturally occurring isotopes of the element

4 different ways of element notation 1. 2. 4He 3. He-4 4. Helium-4

Ion-an atom or group of atoms that has a positive or negative charge Negative ion (anion)-gained electrons ex. S-2-gained 2 electrons PO4-3-gained 3 electrons Positive ion (cation)-lost electrons ex. Fe+3-lost 3 electrons NH4+1-lost 1 electron

Element/Ion C-12 C-13 C-14 #p #n #e Atomic mass At. # Mass # Isotope-atoms of the same element that have the same atomic number (same # of protons) but different mass number due to a different number of neutrons Element/Ion C-12 C-13 C-14 #p #n #e Atomic mass At. # Mass # 6 6 6 6 8 7 6 6 6 12.011 12.011 12.011 6 6 6 14 12 13

So…let’s put it all together and attempt to fill in a chart Element/ Ion Atomic Mass No. # p # n # e Ca 40.08 20 20 20 20 40 51 71 51 122 51 Sb 121.760 N-3 14.0067 7 7 7 10 14 52 Te+6 52 76 127.60 46 128

Element Mass # Atomic # p #n # e Ar-36 36 39.948 18 Ar-38 38 20 Ar-40 Watch out for isotopes. The atomic mass and the mass number will not correspond to each other Element Mass # Atomic # p #n # e Ar-36 36 39.948 18 Ar-38 38 20 Ar-40 40 22

Remember our definition of atomic mass-the weighted average of the masses of the naturally-occurring isotopes of that element. So…how do they determine an atomic mass? Ex. Cl-35 has an abundancy of 75.77 % and Mass of 34.969 Cl-37 has an abundancy of 24.23% and Mass of 36.966 Since it is a weighted average: (34.969)(75.77) + (36.966)(24.23) = 35.454 100 Check your periodic table now!

The location of an atom’s electrons is called electron configuration It becomes important to chemists to know the location of an atom’s electrons. The location of an atom’s electrons is called electron configuration There are 3 methods: Diagonal Method Arrow Method Lewis Dot All three methods depend on the fact that you know The Diagonal Rule

The Diagonal Rule

What does each number/letter represent? Maximum no. of < electrons (can have less) Principle Energy level  (1-7) ^ Sublevel (s, p, d or f)

The part of the atom exclusive of its valence electrons Kernel- The part of the atom exclusive of its valence electrons (the nucleus + all inner electrons) Valence electrons- The electrons in the outermost shell (valence shell) of an atom

The condition of an atom or ion in which the electrons Ground state The condition of an atom or ion in which the electrons occupy the lowest available energy levels Excited state The condition that exists when the electrons of an atom occupy higher energy levels while lower energy levels are vacant Ground state Excited state

How does an electron become excited? Electrons absorb energy and temporarily move to a higher energy level. The electron quickly returns to a lower available level emitting the same amount of energy it absorbed to go to the higher energy level. This energy is seen as light. While the light appears as one color, it is actually composed of many different wavelengths, each of which is seen as a different line when viewed through an instrument called a spectroscope.

and these spectra are used to identify elements Each atom has its own distinct pattern of emission lines (or bright line spectrum) and these spectra are used to identify elements

3 Types of Matter 1. Element- The simplest form of matter that has a unique set of properties; an element cannot be broken down into simpler substances by chemical means. A substance that contains two or more elements chemically combined in a fixed proportion. Can be separated by chemical means 2. Compound- 3. Mixture- A physical blend of two or more substances that are not chemically combined. Can be separated by physical means.

that we can refer to as substances? ANSWER: ELEMENTS & COMPOUNDS Matter that has uniform and definite composition; also called pure substance Based on our definitions of element, compound, mixture and substance, what are the only things that we can refer to as substances? ANSWER: ELEMENTS & COMPOUNDS

Based on the distribution of their components, elements compounds and mixtures can be classified as either homogeneous or heterogeneous Homogeneous-a mixture that is uniform in composition; components are evenly distributed and not easily distinguished. Heterogeneous-a mixture that is not uniform in composition; components are not evenly distributed throughout the mixture.

Elements Copper Nickel

Compounds Aluminum oxide Sodium chloride

Mixtures Rocky road ice cream Soil suspension Vinegar solution

Based on our definitions and the pictures we saw, what types of matter are homogenous? Elements Compounds Mixtures-solutions only Based on our definitions and the pictures we saw, What types of matter are heterogeneous? Mixtures-but not solutions

How do we describe matter and the changes that matter undergoes? We describe matter based on its physical and chemical properties and the physical and chemical changes that it undergoes.

Physical Property- Those characteristics that can be observed without the production of a new substance. Ex.: color odor taste hardness density melting point boiling point conductivity ductile (can be drawn into wires) malleable (can be hammered into sheets) luster (shine)

Chemical property- Characteristics that describe how the substance interacts (or fails to interact) with other substances to produce new substances. Ex.: reactivity flammability combustibility (no longer have the original substance and can’t get it back)

Physical Change- When one or more physical properties of a substance are changed but without any change in the substance’s chemical properties or composition. Ex.: change of color grinding of substance magnetizing of iron melting boiling dissolving

Chemical change- Any change that results in the production of one or more substances that differ in chemical properties and composition form the original substance Ex. rusting of iron souring of milk burning of paper

Law of Conservation of Energy- In any chemical or physical process, energy is neither created nor destroyed Law of Conservation of Matter/Mass In any physical or chemical reaction, mass is conserved; mass can be neither created nor destroyed. Mass of reactants = Mass of products 2H2 + O2  2H2O 4 g 32 g 36 g

Physical Means of Separation Filtration-a process that separates a solid from the liquid in a heterogeneous mixture

The separation of mixtures into their constituents by Chromatography The separation of mixtures into their constituents by preferential adsorption

Distillation/Fractional Distillation A process used to separate dissolved solids from a liquid, which is boiled to produce a vapor that is then condensed into a liquid