Chemistry Unit 3

6. Element 98 californium (Cf) is in period 7 three squares to the right of curium (Cm). Cf was synthesized in 1950 at the University of California. Select its most likely density from the following: 7.8 g/cm3, 12.4 g/cm3, or 15.1 g/cm3? Explain your selection.(L8)

15.1 g/cm3. The densities appear to increase as you move from left to right.

3. The periodic table shows the number 5 and the number 10.81 in the same square as the element with the symbol B. Which of those numbers is the atomic number? (L4)

5 is the atomic number. Atomic numbers are always whole numbers.

2a. What is the atomic number of nitrogen?(L4)

7 is the atomic number of nitrogen.

5. Element 41 niobium (Nb) is in period 5 under vanadium (V). It is a metal found in steel cutting tools. Select its most likely density from the following: 2.33 g/cm3, 5.43 g/cm3, or 8.57 g/cm3. (L8)

8.57 g/cm3. It is in period 6 and as one moves down the rows the densities tend to increase.

1.5

A compound is a substance that is made of more than one kind of atom chemically combined. For example, water is a compound that combines two atoms of hydrogen with one atom of oxygen to make one molecule of water.

2a. Is a hydrogen neutron the same as an aluminum neutron? (L4)

A neutron is a neutron no matter the type of atom.

3. Is a hydrogen proton the same as an aluminum proton? (L4)

A proton is a proton. The number of protons determines the atom's identity.

Lesson 2e.

A scientific theory is based on scientific laws and facts. Scientific theories result from the work of many scientists who test, confirm, and reconfirm the outcome of their combined work. Scientific theoriesprovide the basis for making predictions and explaining scientific events and phenomena. Examples of scientific theoriesare atomic theory, cell theory, plate tectonics, and the germ theory of disease.

Statement 6.(L2)

Agree. Atomic theory states that all matter is made of tiny particles called atoms. This is the first premise of Dalton's Atomic Theory.

Statement 11.(L2)

Agree. Atomic theory states that atoms are the smallest particles that an element can be divided into and still have the characteristic properties of that element.

Statement 2. (L2)

Agree. Scientific laws are based on observations.

Statement 3. (L2)

Agree. Scientific laws are based on scientific facts.

Statement 7.(L2)

Agree. Scientific theories help scientists explain observations.

1.9

All elements have a chemical symbol. The chemical symbol is used to represent the elements in chemical formulas. For example, water is chemically known as H2O. H2O is water's chemical formula. The symbols for hydrogen (H) and oxygen (O) tell us that water is made from these elements. The two after the hydrogen symbol (H2) tells us that each molecule of water contains two atomsof hydrogen. Since there is no number after oxygen, each molecule of water contains only one atom of oxygen.

Lesson 5a.

Although electrons are in constant motion, they do not "orbit" the nucleus as is sometimes shown in pictures and models. Instead, they move about in cloud-like regions.

1. Use your data and the class data to order the densities of zinc, lead, aluminum, and iron from least dense to most dense. (L8)

Aluminum is the least dense, zinc is the second least dense, iron is the second densest, and lead is most dense.

What is in an atom?

An atom is the smallest unit of an element. We have subatomic particles; the protons, the neutrons, and the electrons. At the center of the atom, there is the nucleus, which have protons and neutrons, and the electrons are outside.

What is an ion?

An ion is a positively or negatively charged atom, and in an ion, the number of electrons can change.

4. When you read about elements, you will see the word "ion". Does anyone know what an "ion" is? (L4)

An ion is an atom that has gained or lost electrons. Thus, the atom will have a positive or negatively charged.

2d. Aluminum and Argon: (L8)

Argon is a gas and less dense than aluminum.

Lesson 8b.

As you move across each period, atomic numbers increase by one and the average mass numbers increase. The number of electrons also increase. But, more importantly there are cyclic variations in the characteristic properties of the atoms.

1.15

Atomic modelsaid in understanding the physical and chemical properties of the elements. The wave mechanical model of the atom is currently the most useful to describe the arrangement of particles within an atom.

Lesson 4a.

Atoms have mass or weight. Their mass comes from the fundamental particles found in the atom's center or nucleus.Two kinds of fundamental particles are located in the nucleus. They are called protons and neutrons.

2. What is a neutral atom?(L4)

Atoms with the same number of protons (+ charges) and electrons (- charges) are neutral.

1.10

Atomsare composed of smaller sub-atomic or fundamental particles called protons, neutrons, and electrons. • Protons and neutrons are found in the atom's nucleus. • Protons are positively charge particles (+ charge). • Neutrons are neutral particles (no charge) about the size of a proton. Note: Neutrons are slightly more massive than protons. • Electrons are negatively charged particles (- charge) that move about the nucleus. Electrons can also move from atom to atom given the right circumstances. • Electronsare infinitesimal in size as compared to protons and neutrons. Electrons are not included in the mass numbers. • Electrons are found in regions or energy levels outside the nucleus. • The number and arrangement of electrons outside the nucleus accounts for the atom's reactivity with the atoms of other elements.

2a. Hydrogen and Helium: (L8)

Both are gases. Hydrogen is less dense that helium.

2c. Calcium and Zinc: (L8)

Calcium is less dense than zinc.

Lesson 8c.

Densityis a characteristic property of elements and compounds. Density compares the mass of a substance to its volume. Density is calculated by dividing the mass of an object by its volume.

Statement 8.(L2)

Disagree. Scientific laws are very similar to the laws made by government. Scientific laws are very different. Scientific laws are not rules that can be changed or altered.

Statement 1. (L2)

Disagree. Scientific laws can be changed. Scientific laws are not changeable.

Statement 4. (L2)

Disagree. Scientific theories have little basis in fact. They are all based on facts.

Statement 5. (L2)

Disagree. Scientific theories lead to scientific laws.Scientific laws lead to scientific theories. Theories combine or synthesize scientific laws.

Statement 10.(L2)

Disagree. Simply put, scientific theories are conjectures or guesses made by scientists that have no basis in fact. Scientific theories are based on scientific laws and facts. They are not guesses or conjectures that are easily altered.

Statement 9.(L2)

Disagree.An example of a scientific law is atomic theory. An example of a scientific law is the law of gravity. Atomic theory is an example of a scientific theory.

Lesson 4d.

Electrons, a third fundamental particle of atoms, are not found in the nucleus. They are found in regions called energy levelsoutside the nucleus. Thus, atoms are sometimes described as having a centralnucleus with an electron cloudoutside the nucleus. Electrons have a very, very small mass as compared to protons and neutrons. Their mass is so small that it is not included in the mass of an atom. Electrons have a negative (-) charge equal in magnitude but opposite to the positive (+) charge of a proton. Because of their negative charge, electrons are sometimes represented with a (-) sign. An electrically neutral atom has the same number of protons (+ charges) and electrons (- charges). Unlike protons and neutrons, electrons are constantly in motion. In chemical changes, atoms can gain electrons, lose electrons, or share electrons.

1.17

Elements on the periodic table are frequently referred to as either metals or nonmetals. Most of the elements on the periodic table are metals. Metals are usually solids at room temperature, lustrous in appearance, good conductors of heat and electricity, and malleable. Nonmetals,on the other hand, do not have these characteristics and are frequently liquids or gases at room temperature. When metallic atoms combine chemically, they lose or share electrons with nonmetal atoms. Thus, nonmetals generally gain or share electrons with other atoms.

1.16

Elements on the periodic table are organized in periods(horizontal rows), families (vertical columns), and groups (e.g., metals vs. nonmetals) based on their atomic structure.

1. What are the characteristics of a proton? (L4)

From the Reading: (1) found in nucleus, (2) always same number in a specific kind of atom, e.g., hydrogen always has one, (3) has a positive charge (+).

1. What are the characteristics of a neutron? (L4)

From the Reading: (1) found in nucleus, (2) number of neutrons can vary, even in the same atom, (3) no charge and (4) about the same size as a proton.

1. What are characteristics of an electron? (L4)

From the Reading: (1) found in region or cloud outside the nucleus in energy levels, (2) constantly moving, (3) negative charge opposite but equal in magnitude to a proton (4) mass is too small to consider as part of atom's mass, and (5) can be lost to another atom, gained from another atom, or shared with another atom.

1. What is the mass number of an atom? (L4)

From the Reading: Tells the number of protons plus neutrons.

1. What is the atomic number of an atom?(L4)

From the Reading: Tells the number of protons.

2. Where is the nucleus of an atom? (L4)

From the Reading: in the center of an atom

1. What particles are found in the nucleus? (L4)

From the Reading: protons and neutrons

3. Which atom is heavier: gold or silver? (L4)

Gold has 79 protons and silver has 47 protons. Gold has 118 neutrons and silver has 63. Thus, gold's mass number is about 197 (79 +118) and silver's is 108 (47+61). A gold atom is heavier.

3a. The densities of the gases hydrogen (H), helium (He), nitrogen (N), and radon (Rn) are not listed on the density table. Their densities range from 0.00009 g/cm3 to 0.009 g/cm3. Predict which gas has the least density. (L8)

Hydrogen (H)

4. On the periodic table, what is the lightest element? (L4)

Hydrogen because it has 1 proton and no neutrons. All the other atoms have more protons and at least one neutron.

1. Find zinc, lead, aluminum, and iron on your periodic table. Although you have limited data, what are two possible predictions you can make linking the property of density to the organization of the elements on the periodic table?(L8)

I predict as you go across periods the densities increase, and as you go down families the densities also increase.

3. As you move across a period, predict how densities of the elements vary?(L8)

I predict that as you move across the period, the elements get denser.

Compare your results from Part 1 to that of the periodic table. What might account for any differences?(L8)

I think the fact that our graduated cylinders only go up or down by 1 mL accounts for any differences.

What is a neutrally charged atom?

In a neutrally chareged atom, the number of protons and electrons are the same.

Lesson 2b.

In chemistry, a property is an attribute or characteristic of matter like solubility, boiling point, or phase. In science, a theory is based

1.12

Isotopesof an element have the same number of protons but different numbers of neutrons. Isotopes have the same atomic number but different mass numbers.

What is an isotope?

Istotopes are atoms of the same element that can change the number of protons in them.

Lesson 2g.

It pulls together or synthesizes all the currently known scientific laws, facts and observation in a way that enables today's scientists to predict and explain the behavior of matter.

2b. What is the mass number of hydrogen?(L4)

It should be 1 because it has one proton and no neutrons. On the periodic table it is listed as 1.008. This is because one out of every six thousand hydrogen atoms has a neutron.

2. Name a metal that is likely to float in water.(L8)

Lithium, sodium, and potassium all have densities less than 1 and should float on water. These elements are in the upper right-hand corner of the table.

Lesson 1

Matter is composed of atoms. Our evidence for existence of atoms is indirect because no one has ever seen an atom. Is you could observe an atom, you would have direct evidence for its existence. In this investigation you will use indirect evidence to support your claims for the identity of objects in closed containers.

1.3

Modern day chemistry is based on atomic theory. The basic premise of atomic theory is that an atom is the smallest particle of an element that still has the characteristic properties of that element.

1.6.

Molecules are two or more atoms chemically bonded to each other. Molecules of pure substances, like oxygen (O2), are not compounds because they only contain one type of atom.

Lesson 4c.

Neutrons are also found in the nucleus of atoms. Neutron numbers vary in atoms of the same element and from atom to atom. Thus, unlike protons, the same kind of atom can have different numbers of neutrons. An isotope is the name given to atoms with the same number of protons but different numbers of neutrons. For example, hydrogen usually does not have a neutron, but sometimes it does! About one out of every six thousand hydrogen atoms has a neutron. Hydrogen atoms with one neutron are isotopes of hydrogen and are termed heavy hydrogenbecause the neutron adds more mass. Neutrons are about the same mass as a proton. Neutrons do not have a charge.

What are noble gases?

Noble gases are inert and not reactive, since their energy levels are full.

Lesson 2d.

On the other hand, scientific laws are unchangeable, irrefutable, and state a universal truth. Scientific laws are observable and hold true in all situations. Examples of scientific laws are Newton's law of universal gravitation, Newton's laws of motion and the laws of conservation of mass and energy.

Lesson 2c.

On the other hand,scientific laws are unchangeable, irrefutable, and state a universal truth.Scientific laws are observable and hold true in all situations.

Lesson 4b.

Protons are found in the nucleus of all atoms. Each proton has a positive charge (+). It is represented with a plus sign because of its positive charge.

3b. Predict which gas has the greatest density. (L8)

Radon (Rn)

3. How do we know atoms have protons and neutrons? (L4)

Scientists use indirect evidence from experiments to infer the existence of these particles. No one has seen an atom or its particles directly. negative charge. An ion is a charged atom.

2b. If an atom has 13 protons and 14 neutrons, what element does it represent?(L4)

Since the number of protons determines the atomic number, as learned in Lesson Three, an atom that has 13 protons will be aluminum.

2b. Sodium and Aluminum: (L8)

Sodium is less dense than aluminum.

What are columns on the Periodic Table?

The Periodic Table has columns; columns are veryical and also known as families. Columns have similar properties, and the number of the column tells how many electrons are in the outermost electron energy level.

What are rows on the the Periodic Table?

The Periodic Table has rows; rows are horizontal and are known as periods. The number of the row is the number of the electron energy level.

1.8

The Periodic Table of Elements is an essential reference tool for chemists. Elements are displayed on the periodic table in squares. The squares provide valuable information about the elements and their atoms: symbols, atomic numbers, mass numbers and/or average mass numbers.

3. What charge would an atom have if it lost an electron to another atom?(L4)

The atom would still have the same number of protons (+ charges) but one less electron (- charges). The atom would now be positively charged.

1.13

The average mass number is determined by averaging the masses of an atom's isotopes.

Lesson 2f.

The basic premise of both Dalton's atomic theory an dmodern day atomic theory is that atoms are the smallest particles that an element can be divided into and still have the characteristic properties of that element.

2. Which data is most accurate - yours or the class average? (L8)

The class averages are more accurate than that of a single reading from an individual group. Each group could be considered one trial.

4. Which statement below is supported by the density values given on the density table on the next page? Explain. a. As you move across a period, the densities increase. b. As you move across a period, the densities decrease. c. As you move across a period, the densities increase, then decrease. (L8)

The correct response is c.

1.14

The mass number is the average mass number rounded to a whole number.

Lesson 4e.

The number of protons added to neutrons determines the atom's mass number.

How do you determine an element?

The number of protons determine the element, and the number of protons are the same.

1.11

The number of protons is the atom's atomic number. The atomic number is unique to each atom and identifies the element.

Lesson 8a.

The periodic table is organized in rows called periods. There are seven periods. The first row or period 1 consists of just two elements: hydrogen and helium. Period 2 begins with lithium and ends with neon. The seventh row starts with francium.

1.2.

The terms law and theory have scientific meanings different from common usage. Scientific laws are unchangeable, irrefutable, and state universal truths. They are observable and hold true in all situations. Scientific theoriesare based on scientific laws and facts. Scientific theories result from the synthesis of many laws and are used to make predictions and explain scientific events and phenomena.

1.7

There are about one hundred and sixteen known elements with eighty-eight occurring naturally (Zumdahl & Decoste, 2011, p. 76). Note: The number of known elements varies based on the reference source and its date of publication because laboratory synthesis of new 7 elements is ongoing. Also, the number of naturally occurring elements may vary from source to source depending on the author's definition of "naturally occuring".

1. Is there any uncertainty (error) in your density measurements? Hint: Are they precise and accurate?(L8)

There is uncertainty in the measurements. More precise tools are available to measure mass and volume. Also, we could have more accurate readings if we would have used multiple trials, and had a solid pure form of each metal.

How do you find the number of neutrons?

To find the number of neutrons, subtract the atomic number from the average mass number.

4. How many protons does iron have? (L4)

Using the periodic table, iron has an atomic number of 26 so it has 26 protons.

Using your observations as indirect evidence, make a claim stating the identity of the object(s) in containers A, B, and C. Support each claim with evidence. (L1)

We think "A" is a small wooden stick with a popcorn kernel, B is a bead, and C is a pebble with napkin and rubber band.

Lesson 2a.

Words that are spelled the same but have different meanings are homonyms.

2e. Zinc and Mercury: (L8)

Zinc is less dense than mercury.