Chemistry Study Guide Midterm Exam

At the surface of Venus, the force of gravity is 0.903 times that on Earth's surface. (a) What would be the mass of a standard 1.00-kg object on Venus? (b) A man who weighs 190 Ib on Earth would weigh how much on the surface of Venus?

(a) 1.00 kg, the mass does not change (b) 190 Ib x 0.903 = 172 Ib

Rutherford's results yielded different than expected outcome

(a) The results that the metal foil experiment would have yielded if Thomson's model had been correct; (b) Actual results

Law of Multiple Proportions

- 1803, John Dalton: Law of Multiple Proportions - Elements may combine in more than one set of proportions, each set corresponds to different compound. - This is how complexity is obtained in world - Nitrous Oxide: "laughing gas" used in dentistry and to increase power output in engines - Nitric Oxide: Signaling molecule in biology and air pollutant - Nitrogen Dioxide N02: Brown gas with sharp odor. Bad air pollutant.

Thomson Experiment

- 1897, Joseph John Thomson: Determined the charge: mass ratio of cathode rays (discovered electrons). - Cathode made of negatively charged particles because they are attracted to a positively charged plate. - The heavier the particle the less is deflected by the electrical field. - He earned the Nobel prize n 1906

Vocabulary word of the day is Proton

- A proton is the kind of particle that is found at a nucleus its charge is positive 1 and its relative mass is 1 - Its mass is about the same as that of a hydrogen atom

Aristotle

- All matter is composed of 4 elements, and all matter is continuous, not atomistic. - 4 elements such as Air, Fire, Earth and Water

Calculate the density of a metal sample with a mass of 18.96g and a volume of 4.31cm^3

- D=mass/volume = 18.96g/4.31cm^3 = 4.40g/cm^3

An 8.00 cm x 2.00 cm x 2.00 cm rectangular bar has a mass of 86.4g will the bar float in water (density = 1.00g/mL) or in mercury (density =13.6g/mL)?

- D=mass/volume =86.4g/(8 x 2 x 2)cm^3 = 86.4/32 = 2.7g/cm^3 - Metal bar will float in mercury

Three Types of Radioactivity

- Discovery of radioactivity also suggested the existence of particles smaller than atoms - Radioactive Chemistry - Alpha particles- heavy nuclei emit He2+ with very high energy. Size of particle limits penetration, i.e. cannot penetrate skin, clothing, etc. • Beta decay- releases high energy electron which is much smaller, can penetrate ~0.5 cm of aluminum • Gamma ray- emission of light at extremely high energy, very dangerous, can easily penetrate entire body. - Gamma is most dangerous

Dmitri Mendeleev (1869)

- Dmitri Mendeleev (1869) organized the elements in a table in order of increasing atomic mass. - Elements were placed in the same column if they had similar chemical properties. - He left gaps for yet undiscovered elements. He predicted the properties of those elements. When those elements were eventually discovered, many of his predictions were found to be accurate

Arrangement of the Periodic Table

- Due to repetitive chemical relationships, vertical columns are called groups or families and horizontal rows called periods. - Periods: Elements in a period demonstrate a range of properties from metallic (on the left) to nonmetallic (on the right). - Groups (families): Groups contain elements with similar chemical properties. Some groups in the periodic table have special names: • Alkali Metals: Group 1A • Alkaline Earth Metals: Group 2A • Halogens: Group 7A • Noble Gases: Group 8A

Electron Arrangement: Nomenclature

- Electron Configurations: Allow us to represent the arrangement of the electrons in an atom.

Electron Arrangement: The Bohr Model

- Flame Tests: Different elements give different colors to a flame. (this is how fireworks are designed). - This suggests that the electrons in the elements have particular properties that correspond with the colors. • White light is all colors together at once. Different colors have different "wavelengths". They can be spread out continuously with a prism (or a rainbow!). Continuous spectrum. • If light from particular elements dispersed with a prism, line spectra are observed. • These lines are due to different energy states for the electrons • Niels Bohr (1913) proposed that electrons have discrete amounts of energy (electrons are quantized). Electrons have energy levels. • A "quantum" is a specific unit by which something must change (like the rungs of a ladder or a tiny unit of energy produced or absorbed when an electron makes a transition from one energy level to another).

Lavoisier: The Law of Conservation of Mass

- Matter is neither created nor destroyed during a chemical change - Chemical reactions are just transformations of matter from one form to another. The atoms simply change the way they are combined together. - When something burned matter is concerned

Proust: The Law of Definite Proportions

- Regardless of the source, copper carbonate has the same composition. - The idea that a compound always contains the same elements in a certain definite proportions.

VOCAB WORD OF THE DAY Chapter 1

- Scientific Hypothesis, are tenable explanations of observed data. - The Hypothesis are tested by designing and performing experiments.

What does Volume mean?

- The volume of a regular shaped solid object can be determined using the volume formula for that geometric shape. - V=lwh

What do those peaks represent?

- They actually represent two isotopes of iron. - One isotope has a mass of 52 another isotope has a mass of 56

How do you find the Density of an Irregularly Shaped Object?

- Use the water displacement method - First find mass in grams - Take a graduated cylinder and add water, then record the volume of water in mL. - Insert the object and read the new volume. - Subtract the new volume of the water displaced will equal to the volume of the object. - Divide the mass by the newly found volume. - equation triangleV = Vf - Vi

Rutherford Gold Foil Experiment

- Using an apparatus similar to that shown, Ernest Rutherford discovered the atomic nucleus. • Over 98% of the alpha particles went straight through • About 2% of the alpha particles went through but were deflected by large angles • About 0.01% of the alpha particles bounced off the gold foil • How can one prove something is empty? • Put something through it - use large target atoms • use very thin sheets of target so do not absorb "bullet" - use very small particle as bullet with very high energy • but not so small that electrons will affect it • bullet = alpha particles, target atoms = gold foil - (a)-alpha particles have a mass of 4 amu & charge of +2 c.u. - gold has a mass of 197 amu & is very malleable

Electron Behavior

- When electrons are in the lowest energy level, they are said to be in the ground state. - When a flame or other source of energy is absorbed by an electron, it is promoted to a higher energy state (excited state) thus absorbing a quantum of energy. - When an electron in an excited state returns to a lower energy state, it emits a quantum of energy also called a photon of energy, which may be observed as light/ color. - Bohr thought the different electron levels corresponded to different electron orbits around the nucleus, similar to the planets orbiting the Sun.

What is a Scientific Theory?

- a set of tested Hypotheses that explain natural phenomena. - Scientific Theories are the best current explanation for natural phenomena. - Theories are always tentative and may change as observations of nature change.

What is Chemistry Matter?

- a study of matter. - matter is anything that has mass - mass is a measure of the quantity of matter an object contains. - mass does not change - but weight can change

Every singel element will have ______

- atoms that have masses that are slightly different

What are Chemical Changes?

- changes in the chemical identity of matter, a new chemical exists after the change - involve reactions in which new substances are formed (chemical identity changes).

Heat

- is energy (not a substance) that can be transfered only from hotter objects to cooler objects. - Heat energy is often measured in calories (cal) or joules (J) - 1 food calorie = 1000cal = 4184 (J) - One calorie (cal) is the amount of heat required to change the temperature of 1.00g of water 1.00 degree Celsius.

Energy

- is the ability to do work or transfer heat - energy is able to change matter either physically or chemically.

What does Density mean?

- the amount of matter in a given amount of space. - equation for Density: d=m/v - some physical quantities are derived from two or more physical measurements - ex: the density of copper is 8.9g/cm^3

Relative Densities

- to determine whether an object will float in a given liquid in which it does not dissolve. - An object will float if its density is less than the density of the liquid.

Valence electrons are

-Valence electrons are the electrons in the outermost principle energy level of an atom. -These are the electrons that are gained, lost, or shared in a chemical reaction. Ex: O 8e- 1S^2 2S^2 2P^4 = 6 valence electrons S 16e- 1S^2 2S^2 2P^6 3S^2 3P^4 = 6e- valence electrons or short hand notation [Ne]3S^2 3P^4 -Elements in a group or family have the same number of valence electrons.

1)How many mm are in 0.05? 2)How many cm are in um?

1) 0.05m x 1000mm/1m =50mm 2) 20um x 1cm/10000um = 0.02cm

What are the three major characteristics for the Scientific Method?

1) Collecting and Analyzing Data by making careful Observations. 2) Developing educated guesses (Hypothesis) as to what happened. 3) Testing the Hypothesis. The Hypothesis are tested by designing and performing experiments. 4) Report the outcome

John Dalton and the Atomic Theory of Matter

1. All matter is composed of extremely small particles called atoms. 2. All atoms of a given element are alike and differ from the atoms of any other element 3. Compounds are formed when atoms of different elements combine in fixed proportions. 4. A chemical reaction involves the rearrangement of atoms.

What are other aspects of the Scientific Method?

1. Self-Correcting 2. Un-biased pursuit of "truth" 3. Anyone can participate 4. Applies universally independent of politics, religion, culture, ethnicity, etc.

Give the Symbols of the elements that occupy the given positions in the periodic table

1. group 13 (IIIA), period 4: Ga 2. group 4 (IVB), period 5: Zr 3. group 1 (IA), period 2: Li 4. group 17 (VIIA), period 4: Br 5. group 11 (IB), period 6: Au

When 6.00 g of carbon is burned in 16.00 g of oxygen, 22.00 g of carbon dioxide is formed. What mass of carbon dioxide is formed when 3.00 g of carbon is burned in 75.00 g of Oxygen?

11.00 g

Goldstein's Experiment: Positive Particles

1886, Goldstein: demonstrated that positive particles migrated in the opposite direction of the electrons. These particles had varying masses and were much larger than electrons.

Electron Charge

1909, Robert Millikan: Using the Oil Drop Experiment, measured the charge of an electron independently. If charge of electrons and mass: charge ratios are know, then one can calculate the mass of an electron. Its mass turned out to be 9.1x10-28 g. yes, one can calculate the mass of an electron

What is the electronic configuration of Li: A. 1s1 B. 1s2 C. 1s3 D. 1s22s1

1S^2 2S^1

What is a compound?

2 or more elements chemically combined

Convert 240nm to Mn Convert 10kg to cg

2.4 x 10^-7 10,000,000

How many electrons are in the 2p orbitals for nitrogen (N)? A)1 B) 2 C) 3 D) 4 E)5 F)6

3

Human body temperature is 37 degree C. Convert this to Kelvin.

37 degree C + 273.15 = 310.15k

How many different elements are listed below? 23X11 22X10 5X11 24X11 12X25

4 different elements

When 5.00g of mercuric oxide decompose, o.370g of oxygen forms. What mass of mercury forms?

5g-0.370 = 4.63g of mercury

What mass of sulfur can react completely with 20.00g of lead? What mass of lead sulfide forms?

?

Summary - Isotope Symbol

A X Z X = Element symbol A = Atomic mass (#protons + #neutrons) Z = Atomic number (# protons)

Modern-day atomic theory Inconsistent:

ALL atom of a given type are identical-- atom CHANGE identity during chemical change processes

Match each element to the appropriate group on the periodic table

Alkali Metal - Potassium - Rubidium Alkaline Earth Metal - Beryllium - Strontium Halogen - Fluorine - Bromine Noble Gas - Argon - Krypton

Classification of Matter is split into

All Matter Mixtures - homogeneous - heterogeneous Pure Substance -elements -compounds

In 1808, John Dalton proposed a series of statements regarding the atom that became known as Dalton's postulates or Dalton's atomic theory. Since Dalton's original proposal, some of the statements have been updated or changed due to new discoveries. Which of the following statements was not a part of Dalton's original atomic theory?

All four statements are part of Dalton's original atomic theory

Which statement describes the Law of Constant Composition (definite proportions)?

All samples of a given chemical compound will be composed of the same elements in the same proportion.

Kelvin scale of Temperature

An absolute scale of temperature in which 0K is the absolute zero of temperature.

In 1904, the English What property of atoms does this experiment demonstrate?

An atom's mass is concentrated in a small volume. This area deflects the positive particles more than 90 degree.

What is the difference between an orbit and an orbital?

An orbit is a fixed path at a definite distance from the nucleus in which the electron revoleves around the nuclues. An Orbital isa region of space around the nucleus where the probablity of finding an electron is at a maximum.

Isotopes are atoms of elements that differ only in their: A. Atomic number B. Nuclear charge C. Number of electrons in the neutral atom D. Atomic mass

Atomic Mass

Leucippus/Democritus 450 BCE

Atomos: Point at which matter can no longer be subdivided.

Atoms: Real and Relevant

Atoms are too small to be observed with the human eye! They are a very real concept. It is even possible to observe computer-enhanced images of atoms. (STM)

Berzelius Demonstrates the Law of Definite Proportions

Berzelius experiment illustrates the Law of Definite Proportions. Original recipe 10.00g of lead + 1.55g of sulfur -> 11.55g of lead sulfide 10.00g of lead + 3.00g of sulfur -> 11.55g of lead sulfide + 1.45g of sulfur (leftovers) 3.00g - 1.45 = 1.55g used up 18.00 g of lead + 1.55g of sulfur -> 11.55g of lead sulfide + 8.00 of lead (leftovers)

Which of the following is an example of the "Law of Multiple Proportions"?

CH4, C2H6, C3H8

Crooks' Cathode Ray

Cathode Ray Tube - a gas discharge tube that would allow electricity to pass through it.

Converting Temperature Units

Celsius degree C = 5/9 (F-32) Fahrenheit degree F = 9/5 degree C + 32 Kelvin (k) = degree C + 273.15

Classify the statements as consistent or inconsistent with modern-day atomic theory.

Consistent - Atoms are the building blocks for all kinds of matter. - Different types of atoms exists - Only whole atoms can participate in chemical reactions Inconsistent - All atoms of a given type are identical - Atoms change identity during chemical change processes.

Modern-day atomic theory Consistent:

Consistent:---Atoms are basic building blocks for all kinds of matter--Different types of atoms exist--only WHOLE atoms can participate in chemical reactions.

Consider a 10-oz glass of water ...

Depending on where you live, water taken from a tap in your home will contain various amounts of the rarer isotopes deuterium, tritium, oxygen-17, oxygen-18.

Discoveries that Led to the Current Atomic Model:

Early 1800's - Volta invented the electrochemical cell (a.k.a the precursor of the modern battery) - Humphry Davy - built a battery to isolate metals. - Michael Faraday - extended the field of electrochemistry.

Metalloids

Elements that may accept or donate electrons readily and possess a mixture of metallic and nonmetallic properties

What is Science Based On?

Evidence, On Observations, and Experimental tests of our assumptions.

Give the name of the element with the electron configuation 1s^2 2s^2 2p^5

Fluorine

Electron Configuration Write the electron configurations for helium (He) sulfur (S), titanium (Ti) and gallium (Ga).

He 2e- 1S^2 S 16e- 1S^2 2S^2 2P^6 3S^2 3P^4 Ti 22e- 1S^2 2S^2 2P^6 3S^2 3P^6 4S^2 3d^2 Ga 31e- 1S^2 2S^2 2P^6 3S^2 3P^6 4S^2 3d^10 4P^1

When 15.00g of mercuric oxide decompose, 1.11g of oxygen forms. What mass of Mercury forms?

HgO -> O2 + Hg, 15.0g = 1.11g + X, X= 13.89g

Which state of matter is composed of particles that are free to move within contact of each other?

Liquid

What is the Scientific Method?

Logical procedure for gathering and testing ideas

Which statement describes the Law of Conservation of Mass?

Mass in an isolated system is neither created nor destroyed by chemical reactions.

Classify each element as a Metal or Nonmetal

Metal - Be - K - Sn Nonmetal - Br - He - S

Leucippus Revisited: Molecules

Molecules are groups of atoms chemically bonded together. A molecule of water is composed of two atoms of hydrogen (H) bonded to an atom of oxygen (O). H2O

Kelvin

No solid substances can be lower than 0 kelvin

When 6.00g of carbon is burned in 16.00g of oxygen, 22.00g of carbon dioxide is formed. What mass of carbon dioxide is formed when 6.00g of carbon is burned in 75.00g of oxygen? a. 6.00g b. 16.00g c. 22.00g d. 81.00g

Original Recipe 6g of carbon + 16g oxygen -> 22g carbon Dioxide =22.00g

Select the pair of elements you would expect to have similar properties

P and N

What is Science?

Process, a search for understanding and explaining natural Phenomenon.

Electron Arrangement: The Quantum Model

Quantum mechanics: sophisticated equations developed in the 1920's to describe the probability of finding an electron in a given volume of space. Quantum model of the atom is based on energy levels that are divided into: principle levels, sublevels, and orbitals. - Principle Energy Levels (Shells): roughly correlate to the distance that an electron is from an atom's nucleus. (n) - Sublevels (subshells): Each principle energy level (n) is divided into sublevels, which represent different electron arrangements. - Orbitals: Orbitals are a region in space representing a high probability of locating an electron. Each sublevel has one or more orbitals.

Vocabulary word of the Day Ch. 1 Scientific Notation

Scientific Notation, a way of writing very large numbers or very small numbers.

What are Scientific Laws?

Summarize large amounts of Scientific Data and Provide Descriptions of Natural Phenomina. (ex: Law of Gravity, Law of Conservation of Mass/Matter) Many Scientists laws can be stated mathematically. (ex: Boyle's Law (PV=k)

Atoms

The Greek Idea

Carbon and oxygen can react to form carbon monoxide (CO) or carbon dioxide (CO2 ) depending on the amount of oxygen available. This illustrates which law? -Law of conservation of mass • Law of definite proportions • Law of multiple proportions • Law of combining elements • The periodic law

The Law of Multiple proportions

The Fact that water from any place on Earth is always 89% oxygen and 11% hydrogen by mass illustrates: a. Democritus' atomic theory b. The Law of definite proportions c. The Law of conservation of mass

The Law of definite proportions

A chemical is placed on a balance in an airtight container. The balance initially reads 250.0g. What will the balance read after the chemical is ignited and completely burned?

The balance will read 250.0g

An orbital can always be described by which of the following? a. The probable location where an electron is found for a particular subshell b. A spherical region where an electron is found c. The path that an electron follows as it orbits the nucleus

The probable location where an electron is found for a particular subshell

Which statement describes the law of multiple proportions?

When two elements react to form multiple compounds, the different masses of one element that combine with a fixed mass of the other element can be expressed as a ratio of whole numbers.

Complete the electron configuration for Ge

[Ar] 4s^2 3d^10 4p^2

What is the metric system?

a decimal system of measurement whose units are based on certain physical standards and are scaled on multiples of 10

Vocab word of the day is Molecule

a molecule is a group of atoms chemically bonded together.

Which of the following events involve chemical changes and which involve physical changes? a. A steel wrench left out in the rain becomes rusty b. A stick of butter melts c. A wooden log is burned d. A piece of wood is ground up into sawdust

a. chemical change b. physical c. chemical d. physical

Which of the following represent elements and which represent compounds? a. C b. Ca c. HI d. BN e. In f. HBr

a. element b. element c. compound d. compound e. element f. compound

Which of the elements are metalloids, also known as semimetals?

antimony and arsenic

What are Chemical Properties?

are descriptions of how a substance reacts with another substance. (ex: corrosive, flammable, toxic)

What are Physical Properties?

are observed without any chemical change occurring in the substance. (ex: temperature, mass, color, boiling point, odor, taste.)

What are Physical Changes?

changes in the physical structure of matter, the same chemicals exist after the change

when the electron falls back

closer to the nucleus

electron higher state

farther away

What is a Pure Substance?

has a definite (fixed) composition that does not vary from one sample to another.

Temperature

is a measure of the amount of heat in an object

What is a Theory?

is an explanation of observations that has experimental evidence to support it.

What is Chemistry?

is the discipline of science that deals with the study of matter, its properties, its changes and the energy associated with these changes.

THE VOLUME OF A SILVER SPOON IS 15.0CM^3 and its density is 10.5g/cm^3. What is the mass of the silver spoon?

m= 15.0 cm^3 x 10.5g/cm^3= 157.5g or 158g

Elements within groups exhibit similar chemistry due to: a. similarities in electron arrangement b. similarities in nuclear arrangement c. similarities in both electron and nuclear arrangement d. similarities in only the number of protons in the nucleus

similarities in electron arrangement

What are the different types of Matter?

solid, definite shape and volume liquid, definite volume but no definite shape gas, no definite shape nor volume

Isotopes

• All atoms of an element are identical in atomic number but not in mass number. • Isotopes are two or more forms of the same element (same number of protons) whose atoms differ in number of neutrons, and hence in mass. • Isotopes are identified by their mass numbers. - mass number = protons + neutrons • The average of the masses of its naturally occurring isotopes weighted according to their abundance, is what is going to give an element, its atomic mass. - All carbon atoms have 6 protons, BUT not all carbon atoms have 6 neutrons. - 98.89% of the naturally occurring carbon atoms have 6 neutrons in their composition. - 1.11% have 7 neutrons - less than 0.01% have 8 neutrons Isotopes of carbon: C-12, C-13, C-14 also written as: 12^C 13^C 14^C - Isotopes of hydrogen: 1H 2H 3H Natural Abundance 99.98% 0.02% 1.0x10-16 % - Isotopes of oxygen: 16O 17O 18O Natural 99.76% 0.04% 0.20% Abundance

Thomson's Atomic Model

• Atom has structure • Electrons suspended in a positively charged electric field - must have positive charge to balance negative charge of electrons and make the atom neutral • Mass of atom due to electrons • Atom mostly "empty" space

Orbitals

• Each orbital can only hold a maximum of two electrons. • Each subshell contains orbitals with the same letter designation (s, p, d, f, etc.) - Electron Arrangement: Orbitals overlap, Centered on the nucleus

Electron Configurations and the Periodic Table

• Metals, Nonmetals, and Metalloids - Metals: • metallic luster, conduct heat and electricity, malleable and ductile. Ex: sodium, copper - Nonmetals: dull luster, nonconductors, brittle Ex: sulfur, bromine - Metalloids • Demonstrate properties of both metals and nonmetals. Ex: silicon, arsenic

Today's View of the Atomic Model

• The atom contains a tiny dense center called the nucleus • The nucleus is only about 10-13 cm in diameter. • The nucleus is essentially the entire mass of the atom • The nucleus is positively charged • The electrons move around in the empty space of the atom surrounding the nucleus

Structure of the Nucleus

• The nucleus was found to be composed of two kinds of particles: - Protons • charge = +1 • mass is about the same as a hydrogen atom - Neutron • has no charge • has a mass slightly more than a proton

Atoms are easily weighed

• This is the mass spectrum for iron (Fe), which has two major forms, weighing 52 and 56 atomic mass units

Electron Properties

• Thompson could measure the mass/charge ratio for electrons • He could not measure the mass or the charge independently, leaving the true nature in doubt i.e. did all electrons have the same mass? -and what was it?