Periodic Trends 1 of 31 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. 2 of 31 1
Periodic Trends > Trends in Atomic Size Trends in Atomic Size What are the trends among the elements for atomic size? 3 of 31 Periodic Trends > 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. 4 of 31 2
Periodic Trends > 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. 5 of 31 Periodic Trends > Trends in Atomic Size 6 of 31 3
Periodic Trends > Trends in Atomic Size 7 of 31 Periodic Trends > Ions Ions How do ions form? 8 of 31 4
Periodic Trends > Ions Positive and negative ions form when electrons are transferred between atoms. 9 of 31 Periodic Trends > Ions Positive and negative ions form when electrons are transferred between atoms. 10 of 31 5
Periodic Trends > 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. 11 of 31 Periodic Trends > Ions Animation 7 Discover the ways that atoms of elements combine to form compounds. 12 of 31 6
Periodic Trends > Trends in Ionization Energy Trends in Ionization Energy What are the trends among the elements for first ionization energy, ionic size, and electronegativity? 13 of 31 Periodic Trends > Trends in Ionization Energy The energy required to remove an electron from an atom is called ionization energy. 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. 14 of 31 7
Periodic Trends > Trends in Ionization Energy Group and Periodic Trends in Ionization Energy First ionization energy tends to decrease from top to bottom within a group and increase from left to right across a period. 15 of 31 Periodic Trends > Trends in Ionization Energy 16 of 31 8
Periodic Trends > Trends in Ionization Energy 17 of 31 Periodic Trends > Trends in Ionization Energy 18 of 31 9
Periodic Trends > Trends in Ionic Size Trends in Ionic Size During reactions between metals and nonmetals, metal atoms tend to lose electrons, and nonmetal atoms tend to gain electrons. The transfer has a predictable effect on the size of the ions that form. 19 of 31 Periodic Trends > Trends in Ionic Size Cations are always smaller than the atoms from which they form. Anions are always larger than the atoms from which they form. 20 of 31 10
Periodic Trends > Trends in Ionic Size Relative Sizes of Some Atoms and Ions 21 of 31 Periodic Trends > Trends in Ionic Size Trends in Ionic Size Size generally increases 22 of 31 11
Periodic Trends > Trends in Electronegativity 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. 23 of 31 Periodic Trends > Trends in Electronegativity Representative Elements in Groups 1A through 7A 24 of 31 12
Periodic Trends > Summary of Trends Summary of Trends What is the underlying cause of periodic trends? 25 of 31 Periodic Trends > Summary of Trends The trends that exist among these properties can be explained by variations in atomic structure. 26 of 31 13
Periodic Trends > Summary of Trends Ionic Atomic Electronegativity Size Shielding Ionization Nuclear of size Size cations anions Charge energy Decreases Constant Increases Increases Decreases 27 of 31 14