Classifying Periodic Elements

Classifications of Periodic Elements

Metals

• Typically found on the left side and center of the periodic table
• Characteristics:
  • High electrical and thermal conductivity
  • Malleable and ductile
  • High density
  • React with nonmetals to form ionic compounds
  • Tend to lose electrons to form cations
• Examples: sodium (Na), iron (Fe), copper (Cu)

Nonmetals

• Typically found on the right side of the periodic table
• Characteristics:
  • Low electrical and thermal conductivity
  • Brittle and non-ductile
  • Low density
  • React with metals to form ionic compounds
  • Tend to gain electrons to form anions
• Examples: carbon (C), nitrogen (N), oxygen (O)

Alkaline Earth Metals

• Group 2 elements
• Characteristics:
  • Less reactive than alkali metals
  • Tend to lose two electrons to form a +2 cation
  • High melting and boiling points
  • React with nonmetals to form ionic compounds
• Examples: magnesium (Mg), calcium (Ca), strontium (Sr)

Noble Gases

• Group 18 elements
• Characteristics:
  • Unreactive due to full outer energy level
  • Low melting and boiling points
  • Low reactivity
  • Do not react with other elements to form compounds
• Examples: helium (He), neon (Ne), argon (Ar)

Ionisation Enthalpy

• Energy required to remove an electron from an atom
• Increases from left to right across a period
• Decreases down a group
• Important in determining chemical reactivity

Electron Gain Enthalpy

• Energy released when an electron is gained by an atom
• Increases from left to right across a period
• Decreases down a group
• Important in determining chemical reactivity

Atomic Radii

• Distance from the nucleus to the outermost electron
• Decreases from left to right across a period
• Increases down a group
• Affects chemical reactivity and bonding

Ionic Radii

• Distance from the nucleus to the outermost electron in an ion
• Cations (positive ions) are smaller than parent atoms
• Anions (negative ions) are larger than parent atoms
• Affects chemical reactivity and bonding

Electronegativity

• Ability of an atom to attract electrons in a covalent bond
• Increases from left to right across a period
• Decreases down a group
• Affects chemical reactivity and bonding
• Important in determining polarity of molecules

Characteristics of Periodic Elements

Metals

• Found on the left side and center of the periodic table
• Have high electrical and thermal conductivity
• Are malleable and ductile
• Have high density
• React with nonmetals to form ionic compounds
• Tend to lose electrons to form cations
• Examples: sodium (Na), iron (Fe), copper (Cu)

Nonmetals

• Found on the right side of the periodic table
• Have low electrical and thermal conductivity
• Are brittle and non-ductile
• Have low density
• React with metals to form ionic compounds
• Tend to gain electrons to form anions
• Examples: carbon (C), nitrogen (N), oxygen (O)

Alkaline Earth Metals

• Are Group 2 elements
• Are less reactive than alkali metals
• Tend to lose two electrons to form a +2 cation
• Have high melting and boiling points
• React with nonmetals to form ionic compounds
• Examples: magnesium (Mg), calcium (Ca), strontium (Sr)

Noble Gases

• Are Group 18 elements
• Are unreactive due to full outer energy level
• Have low melting and boiling points
• Have low reactivity
• Do not react with other elements to form compounds
• Examples: helium (He), neon (Ne), argon (Ar)

Periodic Trends

Ionisation Enthalpy

• Is the energy required to remove an electron from an atom
• Increases from left to right across a period
• Decreases down a group
• Is important in determining chemical reactivity

Electron Gain Enthalpy

• Is the energy released when an electron is gained by an atom
• Increases from left to right across a period
• Decreases down a group
• Is important in determining chemical reactivity

Atomic and Ionic Radii

• Atomic radii decrease from left to right across a period
• Atomic radii increase down a group
• Ionic radii: cations are smaller than parent atoms, anions are larger than parent atoms
• Affect chemical reactivity and bonding

Electronegativity

• Is the ability of an atom to attract electrons in a covalent bond
• Increases from left to right across a period
• Decreases down a group
• Affects chemical reactivity and bonding
• Is important in determining polarity of molecules