Ch 2

Alkali metals share the following characteristics ___

They are soft and shiny and have low melting points. They are good conductors of heat and electricity. They react readily with water to form basic solutions.

What rules determine the electronic configuration of an atom?

To write the ground state electronic configuration of an atom, electrons are added to the lowest energy orbitals, giving each orbital two electrons. Electron configuration is shown using superscripts to indicate how many electrons an orbital contains. For example, the electron configuration of the six electrons in a carbon atom is 1s^2 2s^2 2p^2.

The third energy level of electrons around a nucleus ___. The third energy level can hold ___electrons.

d orbitals;18

Ionization energies ___ down a column of the periodic table as the valence electrons get farther from the positively charged nucleus. Ionization energies generally ___ across a row of the periodic table as the number of protons in the nucleus increases.

decrease ;increase

A hydrogen atom with one proton and one neutron, giving them a mass number of two isotope is called

deuterium

The two most common forms of carbon are ___

diamond and graphite.

The ___ is composed of electrons that move rapidly in the almost empty space surrounding the nucleus. It comprises most of the volume of an atom.

electron cloud

The number of valence electrons around an atom is often represented by an ___.

electron-dot symbol

The chemical properties of an element are determined by the number of ___ in an atom.

electrons

A chemical formula uses

element symbols to show the identity of the elements forming a compound and subscripts to show the ratio of atoms (the building blocks of matter) contained in the compound.

The atomic number determines the identity of an ___.

element.

Electrons do not move freely in space; rather, they occupy specific ___ levels.

energy

An electron symbolized by __ and has a ___ charge

e− ; negative

The five halogens, located in group 7A (group 17), include ___

fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and the rare radioactive element astatine (At).

electronic configuration of an individual atom—that is, how the electrons are arranged in an atom's ___. The lowest energy arrangement of electrons is called the ___.

orbitals;ground state

Four nonmetals___comprise 96% of the mass of the human body, and are called the building-block elements

oxygen;carbon; hydrogen;nitrogen;

A proton symbolized by __ and has a ___ charge

p ; positive

A ___ has a dumbbell shape. A p orbital is higher in energy than an s orbital in the same shell because its electron density is farther from the nucleus.

p orbital

The second energy level of electrons around a nucleus ___.The second energy level can hold ___electrons.

p orbitals;8

A row in the periodic table is called a ___. Elements in the same row are similar in size.

period

___ change in a regular way across a row or down a column of the periodic table. Two properties that illustrate this phenomenon are ___.

periodic trends;atomic size and ionization energy

The electrons that surround a nucleus are confined to regions called the ___energy levels or ___.

principal ;shells

An atom is composed of three subatomic particles.

proton,electron,neutron

The nucleus is a dense core that contains the ___. Most of the mass of an atom resides in the nucleus.

protons and neutrons

alkaline earth metals are also shiny solids but less ___than the alkali metals.

reactive

The ionization energy is the energy needed to ___ an electron from a neutral atom. A cation is positively charged, and has fewer __than the neutral atom.

remove ; electrons

An ___ has a sphere of electron density. It is lower in energy than other orbitals in the same shell because electrons are kept closer to the positively charged nucleus.

s orbital

The first energy level of electrons around a nucleus ___.The first energy level can hold ___electrons

s orbital;2

The energy levels consist of a set of orbitals, identified by the letters ___

s, p, d, and f.

Periodic table

A schematic arrangement of all known elements that groups elements with similar properties.

An ___is a region of space where the probability of finding an electron is high. Each ___can hold two electrons.

orbital

Of the ___ elements currently known, ___are naturally occurring and the remaining __have been prepared by scientists in the laboratory.

118 ;90 ;28

s hold ___ , p holds ___, d holds___, and f holds___ electrons

2;6;10;14

The maximum number of electrons is given by the formula ___, where n = the shell number.

2n^2

What are the basic components of an atom?

An atom is composed of two parts: a dense nucleus containing positively charged protons and neutral neutrons, and an electron cloud containing negatively charged electrons. Most of the mass of an atom resides in the nucleus, while the electron cloud contains most of its volume. The atomic number (Z) of a neutral atom tells the number of protons and the number of electrons. The mass number (A) is the sum of the number of protons (Z) and the number of neutrons.

What is an electron-dot symbol?

An electron-dot symbol uses a dot to represent each valence electron around the symbol for an element.

How is the name of an element abbreviated and how does the periodic table help to classify it as a metal, nonmetal, or metalloid?

An element is abbreviated by a one- or two-letter symbol. The periodic table contains a stepped line from boron to astatine. All metals are located to the left of the line. All nonmetals except hydrogen are located to the right of the line. The seven elements located along the line are metalloids.

Determine the number of valence electrons of each element: (a) nitrogen; (b) potassium.

Analysis The group number of a main group element = the number of valence electrons. Solution Nitrogen is located in group 5A, so it has five valence electrons. Potassium is located in group 1A, so it has one valence electron.

Give the period and group number for each element: (a) magnesium; (b) mercury.

Analysis Use the element symbol to locate an element in the periodic table. Count down the rows of elements to determine the period. The group number is located at the top of each column. Solution a. Magnesium (Mg) is located in the third row (period 3), and has group number 2A (or 2). b. Mercury (Hg) is located in the sixth row (period 6), and has group number 2B (or 12).

___ contains 60 carbon atoms joined together in a sphere of 20 hexagons and 12 pentagons in a pattern that resembles a soccer ball.

Buckminsterfullerene also referred to as a bucky ball,

___is hard because it contains a dense three-dimensional network of carbon atoms in six-membered rings.

Diamond

Rules to Determine the Ground State Electronic Configuration of an Atom

Electrons are placed in the lowest energy orbitals beginning with the 1s orbital.Each orbital holds a maximum of two electrons.

How are electrons arranged around an atom?

Electrons occupy discrete energy levels (numbered 1, 2, 3, and so on) that contain orbitals (s, p, d, and f). Each orbital can hold two electrons.

How is the location of an element in the periodic table related to its number of valence electrons?

Elements in the same group have the same number of valence electrons.

___ is a slippery black substance used as a lubricant. It contains parallel sheets of carbon atoms in flat six-membered rings.

Graphite

Water is formed from two hydrogens for each oxygen, so its formula is

H2O

What are isotopes and how are they related to the atomic weight?

Isotopes are atoms that have the same number of protons but a different number of neutrons. The atomic weight is the weighted average of the mass of the naturally occurring isotopes of a particular element.

___have properties intermediate between metals and nonmetals. Only seven elements are categorized as one of this: boron (B), silicon (Si), germanium (Ge), arsenic (As), antimony (Sb), tellurium (Te), and astatine (At).

Metalloids

___are shiny substances that conduct heat and electricity. They are ductile, meaning they can be drawn into wires, and malleable, meaning they can be hammered into shapes.

Metals

Table salt is formed from sodium (Na) and chlorine (Cl) in a ratio of 1:1, so its formula is

NaCl.

___do not have a shiny appearance, and they are generally poor conductors of heat and electricity. Like sulfur and carbon they are solids at room temperature; bromine is a liquid; and nitrogen, oxygen, and nine other elements are gases.

Nonmetals

How are atomic size and ionization energy related to location in the periodic table?

The size of an atom decreases across a row and increases down a column. Ionization energy—the energy needed to remove an electron from an atom—increases across a row and decreases down a column.

What are the basic features of the periodic table?

The periodic table is a schematic of all known elements, arranged in rows (periods) and columns (groups), organized so that elements with similar properties are grouped together. The vertical columns are assigned group numbers using two different numbering schemes: 1-8 plus the letters A or B; or 1-18. The periodic table is divided into the main group elements (groups 1A-8A), the transition metals (groups 1B-8B), and the inner transition metals located in the two rows below the main table

The ___ and the ___ earth elements are located on the far left side of the periodic table. Although ___ is also located in group 1A, it is not an alkali metal.

alkali; alkaline ;hydrogen

Isotopes

are atoms of the same element having a different number of neutrons.

Since the mass of an individual atom is so small (on the order of 10^-24 g), chemists use a standard mass unit, the ___, which defines the mass of individual atoms relative to a standard mass.

atomic mass unit

The ___ tells us how many electrons must be placed in orbitals.

atomic number

All matter is composed of the same basic building blocks called

atoms

Opposite charges ___while like charges ___each other.

attract ; repel

Sometimes the spheres will be connected by "sticks" to generate a ___representation for a compound. At other times, the spheres will be drawn close together to form a ___representation.

ball-and-stick ; space-filling

The six alkaline earth elements, located in group 2A (group 2), include ___

beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra).

___ ability to join with itself and other elements gives it versatility not seen with any other element in the periodic table

carbon

Removing an electron from a neutral atom forms a ___.

cation

Elements that comprise a particular group have similar ___ .

chemical properties

The shells are numbered, n = 1, 2, 3, 4, and so forth, beginning ___to the nucleus. Electrons ___to the nucleus are held more tightly and are lower in energy. Electrons ___from the nucleus are held less tightly and are higher in energy.

closest ;closer ;farther

A column in the periodic table is called a___ .Elements in the same group have similar electronic and chemical properties.

group

In their elemental form, ___contain two atoms joined together—F2, Cl2, Br2, and I2.

halogens

The ___ gases are located on the far right side of the periodic table.

halogens and noble

The group number (using the 1A-8A system) equals the number of valence electrons for main group elements (except ___).

helium

The six noble gases, located in group 8A (group 18), include ___

helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and radon (Rn).

To identify the electrons in the valence shell, always look for the shell with the ___ number

highest

The size of atoms ___down a column of the periodic table, as the valence electrons are farther from the nucleus.The size of atoms ___ across a row (left to right) of the periodic table as the number of protons in the nucleus increases. An increasing number of protons pulls the electrons closer to the nucleus, so the atom gets smaller.

increases ;decreases

The ___ elements consist of the lanthanides and actinides, and they are not assigned group numbers.

inner transition metal

An isotope symbol

is also written using the element symbol with the atomic number as a subscript and the mass number as a superscript, both to the left.

The atomic weight

is the weighted average of the mass of the naturally occurring isotopes of a particular element reported in atomic mass units.

The farther an energy level is from the nucleus, the ___its volume becomes, and the more electrons it can hold.

larger

The six alkali metals, located in group 1A (group 1), include ___

lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), and francium (Fr).

The ___ elements consist of the two columns on the far left and the six columns on the far right of the table. These groups are numbered 1A-8A.

main group

Seven other elements, called the ___ , are also present in the body in much smaller amounts (0.1-2% by mass).

major minerals or macronutrients

The number of neutrons =

mass number (A) − atomic number (Z)

The elements in the periodic table are divided into three categories—

metals, nonmetals, and metalloids.

A neutron symbolized by __ and has___ charge

n ; no

___ are especially stable as atoms, and so they rarely combine with other elements to form compounds.

noble gases

Both protons and neutrons contribute to the mass of an atom. The mass number, symbolized by A, is the sum

of the number of protons and neutrons.

Each dot represents __ valence electron. The dots are placed on the ___ sides of an element symbol. For one to ___ valence electrons, single dots are used. With more than __ electrons, the dots are paired.

one ; four; four :four

Each element is identified by a ___letter symbol

one or two

One atomic mass unit (amu) equals ___the mass of a carbon atom that has six protons and six neutrons; 1 amu = ___

one-twelfth; 1.661 × 10^−24 g.

The electronic configuration shows what orbitals contain electrons and uses a ___ with each orbital to show how many electrons it contains.

superscript

the number of positively charged particles =

the atomic number.

The number of protons =

the number of electrons in a neutral atom.

Mass number (A) =

the number of protons (Z) + the number of neutrons.

The atomic number (Z) =

the number of protons in the nucleus of an atom.

The number of neutrons =

the number of uncharged particles.

The chemical properties of a group are similar because these elements contain ___ electronic configuration of valence electrons.

the same

Many other elements occur in very small amounts in the body, but are essential to good health. These___ are required in the daily diet in small quantities, usually less than __ mg.

trace elements or micronutrients;15

The ___ elements are contained in the 10 short columns in the middle of the table, numbered 1B-8B.

transition metal

A hydrogen atoms with one proton and two neutrons, giving them a mass number of three isotope is called

tritium

The chemical properties of an element depend on the most loosely held electrons—that is, those electrons in the outermost shell, called the ___shell. The ___ tells the number of the valence shell.

valence ; period number

Elements in the same group have the same number of ___and similar electronic configurations.

valence electrons