Chemistry Chapter 5

Which has a larger radius, the original neutral atom of an element or that element's anion? why?

The element's anion is larger because it adds an electron to its valence shell which means that the electrons repel each other and therefore make the radius bigger.

Which has a larger radius, the original neutral atom of an element or that element's cation? why?

The element's original neutral atom has a larger radius because the element's cation loses an electron, making it smaller.

Octet Rule:

atoms tend to gain, lose, or share electrons to acquire a full outer energy level of either 2 or 8 electrons

What causes atomic radius to decrease as you go across a period?

the outer electrons are closer to the nucleus and are more attracted to the nucleus. (electrons are added into the same energy level)

Nuclear Charge:

the positive charge of a nucleus (protons pull on electrons)

Shielding Effect:

the presence of more electrons in the lower inner energy levels between the nuclear charge and the valence electrons reduces the effect of nuclear charge on the outer valence electrons

reactivity:

the tendency of a substance to undergo chemical reaction, either by itself or with other materials, and to release energy

Why are noble gases not included in the electronegativity trend?

they already have their full valence shell of electrons; they don't have to grab more electrons.

Why do metals get more reactive as you move down a group?

All alkali metals have one electron in the outer shell. Therefore, the outermost electron gets further from the nucleus. The attraction from the positive nucleus to the negative electron is less. This makes it easier to remove the electron and makes the atom more reactive.

Mendeleev's Periodic Table:

- In order of increasing atomic mass - Grouped elements with similar properties -Left spaces for those not found

Why does ionization energy increase as you move from left to right across a period?

- The # of protons are increasing - electrons are added to same energy level which means that they are pulled closer to the positively charged nucleus.

explain why electronegativity increases as you move across a period

- number of protons is increasing - force of attraction increases - nucleus attracts electrons from other atoms more strongly

explain why electronegativity decreases as you go down a group

- shielding effect happens since there are more inner orbital electrons

Why does ionization energy decrease as you move down a group?

- valence electrons occupy orbitals in higher energy levels - inner electrons shield valence electrons from some of the attraction of protons (nucleus)

Mosely's Periodic Table:

-Worked with Ernest Rutherford examining spectra of different metals -Put in order by atomic # -Had the periodic table organized so that elements with similar proerties were grouped in the same column - When elements are ordered according to increasing # of protons there are periodic patterns in their physical and chemical properties

What three factors affect the trends on the periodic table?

-availablity of electrons - ionic charges - radius size

Test Format:

15-18 MC -History → Mosely and Mendeleev (Know what they did) -Which period and group (atomic number) -Rows and groups (vertical columns and rows; how they work with the trends) -How atomic radius is measured -Definitions of trends -Trends -Predict the ionic charge of the element (look at table on front page of study guide) -Ordering elements (Put them in order to increasing - decreasing value) e.g atomic radius. -Determine which elements are more reactive. Essay Question: (graphic organizer) Explain one of the trends (e.g. Ionization energy, etc...)

Ionic radius trend

As you move across a period ionic radius decreases, except anions have an overall greater radius than cations. As you move down a group ionic radius increases.

Atomic Radius trend

As you move across a period, atomic radius decreases. As you move down a group, atomic radius increases

Which of the following has a larger atomic radius: nitrogen or oxygen? Explain your reasoning beyond their location on the periodic table.

Each oxygen atom has 8 protons in its nucleus, while each nitrogen atom has only 7 protons in its nucleus. Thus, the overall size of the electron cloud of the O molecule is smaller than for N, in part because its electron cloud is drawn in closer to the O nuclei by the greater positive charge on the O nuclei.

What is the most electronegative element on the periodic table?

Fluorine

Anions:

Negative ions; electrons are added (nonmetals)

Cation:

Positive ions; lose electrons (Metals)

Why do nonmetals get more reactive as you move up a group?

These react by losing electrons and reactivity increases as you go down the group. This is because the increased number of electron shells results in more shielding and a greater distance between the outer electrons and the nucleus, which reduces the attraction of the electrons to the nucleus.

Why are anions larger than cations?

anions gain electrons while cations lose electrons

electronegativity trend:

as you move across a period electronegativity increases. as you move down a group electronegativity decreases.

Ionization energy trend:

as you move across a period ionization energy increases. as you move down a family/group Ionization decreases.

Second Ionization Energy:

energy required to move a second electron

Ionization energy:

energy required to remove one electron from a neutral atom of an element

electronegativity:

measure of the ability of an atom in a chemical compound to attract electrons from another atom in the compound

Atomic Radius:

one half the distance between the nuclei of identical atoms that are bonded together

What causes atomic radius to increase as you go down a group?

the number of energy levels increase as you go down the group. (more inner electrons, shielding effect)