Quest Flashcards
Pseudo-noble
Pseudo-noble has electron configuration • elements to the right of silver also form pseudo-noble gas configurations when forming an ion • Gold • Copper • Cadmium • Mercury
Formation of anions
•
an anion is produced when an atom gains one or more valence electrons
• The name fo an anion of a nonmetallic element is NOT the same as the element name
• The name of the element partially ends in -ide
• Chlorine/Chloride oxygen/oxide
• atoms of nonmetallic elements attain noble-gas electrons more easily by gaining electrons than by losing them because these atoms have relatively full valence shells
• Cl 1s^22s^22p^63s^23p^5. Cl^- 1s^22s^22p^63s^23p^6
• the chloride ion has a single negative charge
• Note that the electron configuration of chloride is the same of that of an argon atom
• Chlorine atoms, need one more valence electron to achieve the electron configuration of the nearest noble gas
Halide ions
ions produced when atoms of chlorine and other halogens gain electrons
• All halogens have 7 valence electrons and need only one electron to achieve the noble gas configuration
Formation of Ionic compounds
- an Ionic compound is a compound composed of cations and anions
- Although they are composed of ions and Ionic compounds are electrically neutral
- The total negative charge of the cations equals the total negative charge of the anions
Ionic bonds
the electrostatic forces that hold ions together in Ionic compounds are called Ionic bonds
Chemical formula
a chemical formula shows the number of atoms of each element in the smallest representative unit of a substance
• Sodium chloride = NaCl
• NaCl does not represent a single physical unit
Formation of sodium chloride
sodium cations and chloride anions form a repeating 3-dimensional array in sodium chloride (NaCl)
Formula unit
Ionic compounds do not exist as a single discrete unit, but as a collection of positively and negatively charged ions arranged in repeating patterns
• The chemical formula of an Ionic compound refers to a ratio known as a formula unit
• It is the lowest whole-number ratio of ions in an Ionic compound
Properties of Ionic compounds
most Ionic compounds are crystalline solids at room temperature
• The component ions are arranged in 3-dimensional patterns
• There is a large attraction force since each sodium ion is surrounded by 6 chlorine II s and 6 chlorine ions are surrounded by 6 sodium atoms
• Ionic compounds generally have high melting points
• Because of the arrangement of 6 ions surrounded by 6 ions there is a very strong attraction force and minimal repulsion
• This results in very stable structure
• This stability is reflected in the fact that NaCl has a melting point of about 800 celcius
• Ionic compounds can conduct an electric current when melted or dissolved in water
• The orderly structure breaks down
• If a voltage is applied across this molten mass, cations migrate freely to one electrode and anions migrate to the other
• This allows electric current to flow between the electrodes through an external wire
Coordination number
Coordination Number
• the coordination number is the number of ions of opposite charge that surround the ion in a crystal
• Sodium is surrounded by 6 chloride ions and chloride ions are surrounded by 6 sodium ions therefore the coordination number for sodium and chloride is 6
Metallic Bonds and Metallic Properties
- the valence electrons of atoms in a pure metal can. E modeled as a sea of electrons
- This means that the electrons are mobile and can drift freely from one part of the metal to another
- Metallic bonds are the forces of attraction between the free-floating valence electrons and the positively charged metal ions
Properties of metal
- conductivity
- Ductile
- Malleable
- Low volatility
Crystalline structure of metals
• metals are crystalline
• Metal atoms are arranged in very compact and orderly patterns
• For spheres of identical side, such as metal atoms, several closely packed arrangements are possible
1. Body centered cubic
2. Face centered cubic
3. Hexagonal close-packed
Body centered arrangement
• every atom has 8 neighbors • Metallic elements: - chromium - sodium - potassium - iron - tungsten
Face Centered arrangement
• every atom has 12 neighbors • Examples - gold - copper - silver - aluminum - lead
Hexagonal close-packed crystal structure
• examples:
- zinc
- magnesium
- calcium