Chemistry Chapter 4 Atoms and Elements

How many neutrons are in the nucleus of a bromine atom that has a mass number of 80?

80 - 35 = 45

Arsenic (As)

Needed for growth and reproduction. Quantity needed per kilogram of body weight: 0.050 mg

Study check 4.5 Vanadium is a micronutrient needed in the formation of bones and teeth. Vanadium has two naturally occurring isotopes, V-50 and V-51. Write the atomic symbols for these isotopes of vanadium.

50/23 V and 51/23 V 27 and 28

Quick for first 20 element

Atomic number Period Group

Study check 4.9 Which atom has the largest atomic size, Mg, Ca, or Ci?

Ca

Macromineral

Ca, P, K, Cl, S, Na, and Mg. representative elements located in period 3 and period 4 of the periodic table. They are involved in the formation of bones and teeth, maintenance of heart and blood vessels, muscle contraction, nerve impulses, acid-base balance of body fluids, and regulation of cellular metabolism. The macrominerals are present in lower amounts than the major elements, so smaller amounts are required in our daily diets. It is an element essential to health that is present in the human body in very small amounts (some less than 100 mg)

Study check 4.7 What is the group number of elements with atoms that have five valence electrons

Group 5A (15)

Sample Problem 4.10 Indicate the element in each group that has the higher ionization energy and explain your choice. a. K or Na b. Mg or Cl c. F, N, or C

Na. In Na, an electron is removed from an energy level closer to the nucleus, which requires a higher ionization energy for Na compared to K. Cl. The increased nuclear charge of Cl increases the attraction for the valence electrons, which requires a higher ionization energy for Cl compared to Mg. F. The increased nuclear charge of F increases the attraction for the valence electrons, which requires a higher ionization energy for F compared to C or N.

Iodine (I)

Needed for proper thyroid function. Quantity needed per kilogram of body weight: 0.33 mg

Molybdenum (Mo)

Needed to process Fe and N from food. Quantity needed per kilogram of body weight: 0.20 mg

period 3 electron

Sodium 2,8,1 Sulfur 2,8,6 Argon 2,8,8

Table 4.5 Subatomic Particles in the Atom: ELECTRON

Symbol: e^- Charge: 1- Mass (amu): 0.00055 Location in Atom: Outside Nucleus

Table 4.5 Subatomic Particles in the Atom: NEUTRON

Symbol: n or n^0 Charge: 0 Mass (amu): 1.008 Location in Atom: Nucleus

Table 4.5 Subatomic Particles in the Atom: PROTON

Symbol: p or p+ Charge: 1+ Mass (amu): 1.007 Location in Atom: Nucleus

Table 4.12 Periodic Property: Valence electrons Top to Bottom within a Group Left to Right across a Period

Valence Electrons Remains the same Increase

I is

a halogen

Electron

a negatively charged subatomic particle having a very small mass that is usually ignored in calculations.

Neutron

a neutral subatomic particle having a mass of about 1 amu (atomic mass unit) and found in the nucleus of an atom

Proton

a positively charged subatomic particle having a mass of about 1 amu and found in the nucleus of an atom. Much heavier than electrons

Sample problem 4.7 Using the periodic table, write the group number and the number of valence electrons for each of the following elements: a. cesium b. iodine

a. Cesium (Cs) is in Group 1A (1); cesium has one valence electron. b. Iodine (I) is in Group 7A (17); iodine has seven valence electrons.

Study check 4.2 Strontium is an element that gives a brilliant red color to fireworks. a. In what group is strontium found? b. What is the name of this chemical family? c. In what period is strontium found? d. Is strontium a metal, a nonmetal, or a metalloid?

a. Group 2A (2) b. alkaline earth metals c. period 5 d. metal

Sample Problem 4.6 Write the electron arrangement for each of the following: a. oxygen b. chlorine

a. Oxygen with atomic number 8 has 8 electrons. They are arranged with 2 electrons in energy level 1 and 6 electrons in energy level 2. 2, 6 b. Chlorine with atomic number 17 has 17 electrons, which are arranged with two electrons in energy level 1, eight electrons in energy level 2, and 7 electrons in energy level 3 2, 8, 7

Sample Problem 4.2 Metals, Nonmetals, and Metalloids Use the periodic table to classify each of the following elements by its group and period, group name (if any), and as a metal, a nonmetal, or a metalloid: a. Na, important in nerve impulses, regulates blood pressure b. I, needed to produce thyroid hormones c. Si, needed for tendons and ligaments

a. metal b. nonmetal c. metalloid

Na is

an alkali metal

Number of neutrons in a nucleus =

mass number - number of protons

Copper (Cu) Micromineral

needed for blood vessels, blood pressure, immune system. Quantity needed per kilogram of body weight: 4.0 mg

An atom is electrically neutral

that means that the number of PROTONS in an atom IS EQUAL TO the number of ELECTRONS, which gives every atom an overall charge of zero.

Table 4.12 Periodic Property: Atomic size Top to Bottom within a Group Left to Right across a Period

Atomic Size Increases due to the increase in number of energy levels Decreases due to the increase of protons in the nucleus that pull electrons closer

Sample Problem 4.5 Chromium, a micronutrient needed for maintenance of blood sugar levels, has four naturally occurring isotopes. Calculate the number of protons and number of neutrons in each of the following isotopes: a. 50/24 Cr b. 52/24 Cr c. 53/24 Cr d. 54/ 24

Given: atomic symbos for Cr isotopes Need: number of protons, number of neutrons. Connect: periodic table, atomic number Each isotope of Cr, atomic number 24, has 24 protons. The number of neutrons is found by subtracting the number of protons (24) from the mass number of each isotope. a. 50-24 = 26 b. 52 - 24 = 28 c. 53 - 24 = 29 d. 54 - 24 = 30

Table 4.12 Periodic Property: Metallic character Top to Bottom within a Group Left to Right across a Period

Increases because valence electrons are easier to remove when they are farther from the nucleus Decreases as the attraction of the protons makes it more difficult to remove an electron

Table 4.12 Periodic Property: Ionization energy Top to Bottom within a Group Left to Right across a Period

Ionization Energy Decreases because valence electrons are easier to remove when they are farther from the nucleus Increases as the attraction of the protons for outer electrons requires more energy to remove an electron

Study check 4.10 Arrange Sn, Sr, and I in order of increasing ionization energy.

Ionization energy increases going from left to right across a period: Sr, Sn, I.

Study check 4.11 Of the elements Na, K, and S, which has the most metallic character

K

period 2 electron arrangement

Lithium 2,1 Carbon 2, 4 Neon 2, 8

Nonmetals

Nonmetals are not especially shiny, ductile, or malleable, and they are often poor conductors of heat and electricity. They typically have low melting points and low densities. Some examples of nonmetals are hydrogen (H), carbon (C), nitrogen (N), oxygen (O), chlorine (Cl), and sulfur (S)

Sample problem 4.11 For Na, P, S, Cl, and F, write the symbol for the element that has five valence electrons is in Group 6A (16) has the smallest atomic size has the lowest ionization energy has the most metallic character

P S F Na Na

period 4 electron

Potassium 2,8,8,1 Calcium 2,8,8,2

Cr is

a transition element

Sample Problem 4.9 Identify the smaller atom in each of the following pairs and explain your choice: a. N or F b. K or Kr c. Ca and Sr

a. The F atom has a greater positive charge on the nucleus, which pulls electrons closer, and makes the F atom smaller than the N atom. Atomic size decreases going from left to right across a period. b. The Kr atom has a greater positive charge on the nucleus, which pulls electrons closer, and makes the Kr atom smaller than the K atom. Atomic size decreases going from left to right across a period. c. The outer electrons in the Ca atom are closer to the nucleus than in the Sr atom, which makes the Ca atom smaller than the Sr atom. Atomic size increases going down a group.

Sample Problem 4.3 Subatomic Particles. Indicate whether each of the following is true or false: a. a proton is heavier than an electron b. an electron is attracted to a neutron c. the nucleus contains all the protons and neutrons of an atom

a. true b. false; an electron is attracted to a proton c. true

Sample Problem 4.4 Zinc, a micronutrient, is needed for metabolic reactions in cells, DNA synthesis, the growth of bone, teeth, and connective tissue, and the proper functioning of the immune system. For an atom of zinc that has a mass number of 68, determine the number of: a. protons b. neutrons c. electrons

a30 b. 38 c. 30

Mg is

an alkaline earth metal

Metallic character

an element that has metallic character is an element that loses valence electrons easily. It is more common in the metals on the left side of the periodic table and decreases going from left to right across a period.

Isotopes

are atoms of the same element that have the same atomic number but different numbers of neutrons

Atomic size

determined by the distance of the valence electrons from the nucleus of the atom. For each group of representative elements, the atomic size increases going from the top to the bottom because the outermost electrons in each energy level are farther from the nucleus. Li valence electron in energy level 2 Na has a valence electron in energy level 3 K has a valence electron in energy level 4 all of this means that a K atom is larger than an Na atom, and a Na atom is larger than a Li atom

Period

each horizontal row in the periodic table is a period. The peroids are counted down from the top of the table as Periods 1 to 7

Periodic properties

each property increases or decreases across a period, and then the trend is repeated in each successive period.

Group

each vertical column on the periodic table contains a group (or family) of elements that have similar properties

Metalloids

except for aluminum, the elements located along the heavy line are metalloids. Begin at Group 5 (B, Si, Ge, As, Sb, Te, Po, At, Ts) zigzag line. Metalloids are elements that exhibit some properties that are typical of the metals and other properties that are characteristic of the nonmetals. For example, they are better conductors of heat and electricity than the nonmetals, but not as good as the metals. The metalloids are semiconductors because they can be modified to function as conductors or insulators.

Study check 4.3 T/F: The nucleus occupies a large volume in an atom

false; most of the volume of the atom is outside the nucleus

Metal

in general, most metals are shiny solids, such as copper (Cu), gold (Au), and silver (Ag). Metals can be shaped into wires (ductile) or hammered into a flat sheet (malleable). Metals are good conductors of heat and electricity. They usually melt at higher temperatures than nonmetals. All the metals are solids at room temperature, except for mercury (Hg), which is a liquid

Atomic size trend

increases from top to bottom within a group and decreases from left to right across a period. For representative elements, the atomic size increases going down a group but decreases going from left to right across a period.

Metallic character trend

increases to the left and down. More common in the elements on the left side of the period table and decreases going from left to right across a period. Nonmetals on the right side of the table don't easily lose electrons, which means they are the least metallic.

ionization energy trend

increases up and to the right. The ionization energy decreases going down a group. Less energy is needed to remove an electron because nuclear attraction decreases when electrons are farther from the nucleus

Atomic number

is equal to the number of protons in every atom of that element. Atomic number = number of protons in an atom it is the whole number that appears above the symbol of each element

Group number

is written at the top of each vertical column (group) in the periodic table

Electron arrangement

of an atom gives the number of electrons in each energy level. We can write the electron arrangements for the first 20 elements by placing electrons in energy levels beginning with the lowest.

isotopes are atoms

of the same element that have the same atomic number but different number of neutrons

Study Check 4.6 What element has an electron arrangement of 2,8,5?

phosphorous

What role does iodine play?

proper thyroid function

Lewis symbol

represents the valence electrons as dots, which are placed on the sides, top, or bottom of the symbol for the element. 1-4 valence electrons are arranged as single dots. When an atom has 5-8 valence electrons, 1 or more electrons are paired.

Valence electrons

the chemical properties of representative elements in Groups 1A (1) to 8A (18) are mostly due to valence electrons. These are the electrons in the OUTERMOST ENERGY LEVEL. The group number gives the number of valence electrons for each group of representative elements. All the elements in Group 1A (1) have one valence electron. Group 2A (2) have 2 valence electrons.

Ionization energy

the energy needed to remove an electron from the outermost energy level of an atom, 124-125 Na(g) + energy (ionization) -> Na^+ (g) + e^-

period 1 electron arrangement

the single electron of hydrogen goes into energy level 1, and the 2 electrons of helium fill energy level 1. Thus, energy level 1 can hold just 2 electrons. Hydrogen 1 Helium 2

Atom

the smallest particle of an element that retains the characteristics of that element

Mass number

the total number of protons and neutrons in an atom's nucleus mass number = # of protons + # of neutrons

Atomic symbol

to distinguish between the different isotopes of an element, we write an atomic symbol that indicates the mass number in the upper let corner and the atomic number in the lower left corner

Place the following types of electromagnetic radiation in order of decreasing energy: microwave, ultraviolet, visible, radio waves.

ultraviolet, visible, microwave, radio waves