Chapter 6.3 Chemistry

describe why atomic size decreases within a period?

-Across a period, the electrons are added to the same principal energy level. -The shielding effect is constant for all elements in a period. -The increasing nuclear charge pulls the electrons in the highest occupied energy level closer to the nucleus, and the atomic size decreases.

describe why atomic size increases within a group?

-The increase in positive charge draws electrons closer to the nucleus. -The increase in the number of occupied orbitals shields electrons in the highest occupied energy level from the attraction of protons in the nucleus. -The shielding effect is greater than the effect of the increase in nuclear charge, so the atomic size increases.

what is the least electronegative element?

cesium, with an electronegativity of 0.7. It has the least tendency to attract electrons. When it reacts, it tends to lose electrons and form cations.

In general, first ionization energy generally

decreases from top to bottom within a group.

During reactions between metals and nonmetals, what do metal atoms tend to do and what do nonmetal atoms tend to do?

metal atoms tend to lose electrons and nonmetal atoms tend to gain electrons.

units that form when atoms of the same element are joined to one another.

molecules

The charge for an anion is written as a

number followed by a minus sign

The distance between the nuclei in an iodine molecule is

280 pm.

How are trends in the weather similar to trends in the properties of elements?

Although the weather changes from day to day, the weather you experience is related to your location on the globe.

why is an atom electronically neutral? give an example

An atom is electronically neutral because it has equal numbers of protons and electrons. an atom of sodium (Na) has 11 positively charged protons and 11 negatively charged electrons. The net charge on a sodium atom is zero [(+11) + (-11) = 0].

is an atom or group of atoms that has a positive or negative charge.

An ion

what happens when an atomic number increases within a group? what do these variables affect?

As the atomic number increases within a group, the charge on the nucleus increases and the number of occupied energy levels increases. these variables affect atomic size in opposite ways

why is first ionization energy lower within a group?

As the size of the atom increases, nuclear charge has a smaller effect on the electrons in the highest occupied energy level. Less energy is required to remove an electron from this energy level, and the first ionization energy is lower.

Electrons and the Structure of Atoms Summary

Atomic size, ionization energy, ionic size, and electronegativity are trends that vary across periods and groups of the periodic table. These trends can be explained by variations in atomic structure. The increase in nuclear charge within groups and across periods explains many trends. Within groups, an increase in electron shielding has a significant effect on these trends.

how do atoms of metals tend to form ions?

Atoms of metals, such as sodium, tend to form ions by losing one or more electrons from their highest occupied energy levels

how do nonmetals form ions?

Atoms of nonmetals, such as chlorine, tend to form ions by gaining one or more electrons.

what is the size of a radius in pm for an iodine molecule and why?

Because the atomic radius is one-half the distance between the nuclei, a value of 140 pm (280/2) is assigned to the radius of the iodine atom.

is the ability of an atom of an element to attract electrons when the atom is in a compound.

Electronegativity

describe the chlorine ion (nonmetal)

In a chloride ion, the number of electrons (18) is not equal to the number of protons (17). Because there are more negatively charged electrons than positively charged protons, the chloride ion has a net negative charge.

What are the trends for atomic size?

In general, atomic size increases from top to bottom within a group and decreases from left to right across a period.

What are the trends among the elements for atomic size?

In general, atomic size increases from top to bottom within a group, and decreases from left to right across a period.

What are the trends among the elements for electronegativity?

In general, electronegativity values decrease from top to bottom within a group. For representative elements, the values tend to increase from left to right across a period.

An ion with a positive charge is called a

cation.

What are the trends among the elements for first ionization energy?

First ionization energy tends to decrease from top to bottom within a group and increase from left to right across a period.

describe the group trend in ionic size for the fluoride ion

For example, the radius of a fluoride ion (133 pm) is more than twice the radius of a fluorine atom (62 pm). As the number of electrons increases, the attraction of the nucleus for any one electron decreases.

What are the trends for electronegativity values?

In general, electronegativity values decrease from top to bottom within a group. For representative elements, the values tend to increase from left to right across a period.

describe the sodium ion (metal)

In the sodium ion, the number of electrons (10) is not equal to the number of protons (11). Because there are more positively charged protons than negatively charged electrons, the sodium ion has a net positive charge.

What are the trends among the elements for ionic size?

Ionic size tends to increase from top to bottom within a group. Generally, the size of cations and anions decreases from left to right across a period.

What are the trends for ionic size?

Ionic size tends to increase from top to bottom within a group. Generally, the size of cations and anions decreases from left to right across a period.

what can ionization energies help you predict?

Ionization energies can help you predict what ions an element will form.

describe the difference between removing one electron from Group 1A compared to removing a second electron

It is relatively easy to remove one electron from a Group 1A metal atom, but it is difficult to remove a second electron. This difference indicates that Group 1A metals tend to form ions with a 1+ charge.

describe electronegativity values in metals, nonmetals, and transition metals

Metals at the far left of the periodic table have low values. By contrast, nonmetals at the far right (excluding noble gases) have high values. Values among transition metals are not as regular.

describe group trends in ionic size for metals

Metals that are representative elements tend to lose all their outermost electrons during ionization. Therefore, the ion has one fewer occupied energy level.

What type of element tends to form anions? What type tends to form cations?

Nonmetals tend to form anions. Metals tend to form cations.

electronegativity values are expressed in what units?

Pauling units

How do ions form?

Positive and negative ions form when electrons are transferred between atoms.

is one-half of the distance between the nuclei of two atoms of the same element when the atoms are joined.

The atomic radius

relationship with atomic radius and atomic number

The atomic radius within these groups increases as the atomic number increases.

what is the relationship between atomic size and atomic number

The atomic size increases as the atomic number increases within a group.

describe the group trend in ionic size for the sodium ion

The radius of a sodium ion (95 pm) is about half the radius of a sodium atom (191 pm). When a sodium atom loses an electron, the attraction between the remaining electrons and the nucleus is increased. As a result, the electrons are drawn closer to the nucleus.

In general, the first ionization energy of representative elements increases from left to right across a period. How can this trend be explained?

This trend can be explained by the nuclear charge and the shielding effect. The nuclear charge increases across the period, but the shielding effect remains constant. As a result, there is an increase in the attraction of the nucleus for an electron. Thus, it takes more energy to remove an electron from an atom.

You are familiar with using a weather map to identify trends in the weather. For example, certain areas are typically warmer than other areas. What trends in the properties of elements can you identify with the help of the periodic table?

You can identify trends in atomic size, first ionization energy, ionic size, and electronegativity with the help of the periodic table.

From left to right across a period, two trends are visible for ioniz size —

a gradual decrease in the size of the positive ions (cations), followed by a gradual decrease in the size of the negative ions (anions).

The charge for a cation is written as

a number followed by a plus sign.

An ion with a negative charge is called an

anion.

This size is expressed as an

atomic radius

Electrons can move to higher energy levels when

atoms absorb energy.

what property can be used to predict the type of bond that will form during a reaction.

electronegativity

The distances between atoms in a molecule are

extremely small.

The energy required to remove the first electron from an atom is called the

first ionization energy.

what is the most electronegative element?

fluorine, with a value of 4.0. Because fluorine has such a strong tendency to attract electrons, when it is bonded to any other element it either attracts the shared electrons or forms an anion.

in ionization energy This energy is measured when an element is in its

gaseous state.

period definition

horizontal row (left to right)

In general, the first ionization energy of representative elements.....................

increases from left to right across a period.

Scientists use factors such as __________________ to calculate values for electronegativity.

ionization energy

The energy required to remove an electron from an atom is called

ionization energy.

Some compounds are composed of particles called

ions.

group definition

known as family; columns (up and down)

for nonmetals in group trends in ionic size the ion is much _____________________ than the atom

larger

Anions are always

larger than the atoms from which they form.

If the charge is 1, the number in 1+ is usually ........................ For example, Na1+ is written as

omitted from the symbol for the ion. Na+.

The atomic radius is often measured in

picometers (pm).

the metal and nonmetal transfer of electrons has a

predictable effect on the size of the ions that form.

for metals in group trends in ionic size the ion is much _____________________ than the atom

smaller than the atom.

Cations are always

smaller than the atoms from which they form.

How does the ionic radius of a typical metal compare with its atomic radius?

the atomic radius of a cation metal is bigger

Sometimes the electron has enough energy to overcome

the attraction of the protons in the nucleus.

Because the atoms in each molecule are identical what can be used to estimate the size of the atoms?

the distance between the nuclei of these atoms can be used to estimate the size of the atoms.

One way to think about atomic size is to look at

the units that form when atoms of the same element are joined to one another.

how many picometers are in one meter

there are one trillion, or 1012, picometers in a meter.