# 6.3 Periodic Trends Sodium chloride (table salt) produced the geometric pattern in the photograph. Such a pattern can be used to calculate the position.

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6.3 Periodic Trends Sodium chloride (table salt) produced the geometric pattern in the photograph. Such a pattern can be used to calculate the position of nuclei in a solid. You will learn how properties such as atomic size are related to the location of elements in the periodic table.

Chapter 6 The Periodic Table
6.3 Periodic Trends

Today we are learning to:- 1
Today we are learning to:- 1. Describe trends in the periodic table for atomic size 2. Explain how ions form 3. Describe periodic trends for 1st ionization energy, ionic size and electronegativity

6.3 Trends in Atomic Size The atomic radius is one half of the distance between the nuclei of two atoms of the same element when the atoms are joined. This diagram lists the atomic radii of seven nonmetals. An atomic radius is half the distance between the nuclei of two atoms of the same element when the atoms are joined.

Periodic Trends Atomic Radius Trends in Atomic Size
The are 3 main factors that will have an effect on the size on an atom. Nuclear charge (the charge on the nucleus). A larger positive charge on a nucleus will pull electrons closer to it. The number of the outermost energy level containing electrons. n = 3 is further from the nucleus than n = 2. The number of inner electrons shielding the outer electrons from the nucleus Periodic Trends Atomic Radius

Trends in Atomic Size Group and Periodic Trends in Atomic Size
In general, atomic size increases from top to bottom within a group and decreases from left to right across a period.

6.3 Trends in Atomic Size Size goes UP on going down a group.
Because electrons are added farther from the nucleus, there is less attraction. Size goes DOWN on going across a period. Because of greater nuclear attraction The size of atoms tends to decrease from left to right across a period and increase from top to bottom within a group. Predicting If a halogen and an alkali metal are in the same period, which one will have the larger radius?

6.3

Trends in Ionic Size Positive and negative ions form when electrons are transferred between atoms. When a sodium atom loses an electron, it becomes a positively charged ion. When a chlorine atom gains an electron, it becomes a negatively charged ion. Interpreting Diagrams What happens to the protons and neutrons during these changes?

6.3 Trends in Ionic Size Positive and negative ions form when electrons are transferred between atoms. When a sodium atom loses an electron, it becomes a positively charged ion. When a chlorine atom gains an electron, it becomes a negatively charged ion. Interpreting Diagrams What happens to the protons and neutrons during these changes?

6.3 Trends in Ionic Size Ions
Some compounds are composed of particles called ions. An ion is an atom or group of atoms that has a positive or negative charge. A cation is an ion with a positive charge. An anion is an ion with a negative charge. Metal atoms tend to lose electrons, and nonmetal atoms tend to gain electrons when they react together. The transfer of electrons effects the size of the ions formed Cations are always smaller than the atoms from which they form. Anions are always larger than the atoms from which they form.

up or down when losing an electron to form a cation?
Trends in Ionic Size Does the size go up or down when losing an electron to form a cation?

CATIONS are SMALLER than the atoms from which they come.
Trends in Ionic Size Li + , 78 pm 2e and 3 p Forming a cation. Li,152 pm 3e and 3p CATIONS are SMALLER than the atoms from which they come. There is no longer an electron in the 2s orbital and so size DECREASES.

Does the size go up or down when gaining an electron to form an anion?

ANIONS are LARGER than the atoms from which they come.
Trends in Ionic Size F - , 133 pm 10 e and 9 p F, 71 pm 9e and 9p Forming an anion. ANIONS are LARGER than the atoms from which they come. The electron/electron repulsion in the 2p orbital increases because of the extra electron and so size INCREASES. Trends in ion sizes are the same as atom sizes.

Relative Sizes of Some Atoms and Ions
6.3 Trends in Ionic Size Relative Sizes of Some Atoms and Ions This diagram compares the relative sizes of atoms and ions for selected alkali metals and halogens. The data are given in picometers. Comparing and Contrasting What happens to the radius when an atom forms a cation? When an atom forms an anion?

Trends in Ionic Size

Trends in Ionic Size 6.3 Trends in Ionic Size Size generally increases
The ionic radii for cations and anions decrease from left to right across periods and increase from top to bottom within groups.

6.3

6.3 Trends in Ionization Energy
The energy required to remove an electron from an atom in its gaseous state is called ionization energy. Unit of measurement is KJ/mol (kilojoules per mole) The energy required to remove the first electron from an atom is called the first ionization energy. The energy required to remove an electron from an ion with a 1+ charge is called the second ionization energy. First ionization energy tends to decrease from top to bottom within a group and increase from left to right across a period.

6.3 Trends in Ionization Energy

6.3 Trends in Ionization Energy

6.3 Trends in Ionization Energy
First ionization energy tends to increase from left to right across a period and decrease from top to bottom within a group. Predicting Which element would have the larger first ionization energy—an alkali metal in period 2 or an alkali metal in period 4?

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

Representative Elements in Groups 1A through 7A
6.3 Trends in Electronegativity Representative Elements in Groups 1A through 7A

Electronegativity Nuclear Charge Size of anions Ionic size
6.3 Summary of Trends Electronegativity Nuclear Charge Size of anions Ionic size Ionization energy Shielding Size of cations Atomic Size Decreases Constant Increases Decreases Increases Properties that vary within groups and across periods include atomic size, ionic size, ionization energy, electronegativity, nuclear charge, and shielding effect. Interpreting Diagrams Which properties tend to decrease across a period?

Summary of Trends The succession of elements within a group demonstrates characteristic trends in properties. As you progress down a group: atomic radius increases. electronegativity decreases. first ionization energy decreases. Ionic size increases.

Section Assessment Summary of Trends
The succession of elements within a period demonstrates characteristic trends in properties. As you progress across a group from left to right: atomic radius decreases. electronegativity increases. first ionization energy increases. Ionic size decreases.

1. Which of the following sequences is correct for atomic size?
6.3 Section Quiz 1. Which of the following sequences is correct for atomic size? Mg > Al > S Li > Na > K F > N > B F > Cl > Br

gain electrons to form cations. gain electrons to form anions.
6.3 Section Quiz 2. Metals tend to gain electrons to form cations. gain electrons to form anions. lose electrons to form anions. lose electrons to form cations.

3. Which of the following is the most electronegative?
6.3 Section Quiz 3. Which of the following is the most electronegative? Cl Se Na I

6.3 Section Quiz 4. How does the size of a barium ion compare with the size of a barium atom? The ion is smaller because it has fewer electrons The ion is smaller because it has more electrons The ion is larger because it has fewer electrons The ion is larger because it has more electrons

5. Which ion has the largest radius? Na+ Mg 2+ K + Ca 2+
6.3 Section Quiz 5. Which ion has the largest radius? Na+ Mg 2+ K + Ca 2+

6. Which of the following is the most electronegative?
6.3 Section Quiz 6. Which of the following is the most electronegative? Cl Se Na I

7. Which element has the highest first ionization energy?
6.3 Section Quiz 7. Which element has the highest first ionization energy? sodium aluminum calcium phosphorus

9. Properties of metals include
6.3 Section Quiz 9. Properties of metals include Low ionization energy and high electronegativity Low ionization energy and low electronegativity High ionization energy and high electronegativity High ionization energy and low electronegativity

6.3 Section Quiz 10. An element has a 1st ionization energy of 1314KJ/mol and an electronegativity of It is classified as a metal nonmetal metaloid halogen

1. Which of the following sequences is correct for atomic size?
6.3 Section Quiz 1. Which of the following sequences is correct for atomic size? Mg > Al > S Li > Na > K F > N > B F > Cl > Br

gain electrons to form cations. gain electrons to form anions.
6.3 Section Quiz 2. Metals tend to gain electrons to form cations. gain electrons to form anions. lose electrons to form anions. lose electrons to form cations.

3. Which of the following is the most electronegative?
6.3 Section Quiz 3. Which of the following is the most electronegative? Cl Se Na I

6.3 Section Quiz 4. How does the size of a barium ion compare with the size of a barium atom? The ion is smaller because it has fewer electrons The ion is smaller because it has more electrons The ion is larger because it has fewer electrons The ion is larger because it has more electrons

5. Which ion has the largest radius? Na+ Mg 2+ K + Ca 2+
6.3 Section Quiz 5. Which ion has the largest radius? Na+ Mg 2+ K + Ca 2+

6. Which of the following is the most electronegative?
6.3 Section Quiz 6. Which of the following is the most electronegative? Cl Se Na I

7. Which element has the highest first ionization energy?
6.3 Section Quiz 7. Which element has the highest first ionization energy? sodium aluminum calcium phosphorus

9. Properties of metals include
6.3 Section Quiz 9. Properties of metals include Low ionization energy and high electronegativity Low ionization energy and low electronegativity High ionization energy and high electronegativity High ionization energy and low electronegativity

6.3 Section Quiz 10. An element has a 1st ionization energy of 1314KJ/mol and an electronegativity of It is classified as a metal nonmetal metaloid halogen

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