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
Alloys
- a mixture of two or more elements at least one of which’s a metal
- Copper + zinc = brass
- Copper + tin = bronze
- Steel
- Alloys are important because their properties are often superior to those of their component elements
Substitutional Alloy
• if the atomic sizes are similar the atoms can replace each other
Interstitial Alloy
- if the atomic sizes are quite different, the smaller atoms can fit into the spaces between the larger atoms
- For steel. Carbon toms occupy the spaces between the iron atoms
• elements within each group of the periodic table react in a similar way because they have the same number of _________ _________
Valence electrons
• Valence electrons are the electrons in the __________ occupied energy level of an elements atoms
Highest
• These valence electrons determine the
the chemical properties of an element.
• To find the number of valence electrons in an atom of a representative element simply look at its
•
Group number
- Exceptions to the rule
- atoms of helium have how many valence electrons
- All of the other noble gases have how many valence electrons
- 2
- 8
Electron Dot Structures
- valence electrons are the only electrons involved in chemical bonds
- The valence electrons are shown in electron dot structure
Lewis dot structure
• all noble gases have eight dots because their outer shell is completely full
The Octet rule
• noble gases are ________ or ________ in chemical reactions
stable or non reactive
- The octet rule states that in forming compounds, atoms tend to achieve the electron configuration of noble gases
- An octet is a set of
- Noble gases have _______ electrons in their highest occupied energy level except for ______
- Atoms of metals tend to ____ atoms, leaving a complete octet in the next lowest energy level
- Atoms of some nonmetals tend to _____ electrons or to share electrons with another nonmetal atom or atoms to achieve a complete octet.
- atoms tend to achieve the electron configuration of noble gases
- eight
- eight electrons, helium
- lose
- gain
Formation of cations
• an atom is electrically ______ because it has the same number of _____ and ________
• An ion forms when an atom ______or ______electrons
• A positively charged ion or a cation is produced when an atom _____ one or more valence electrons
- neutral, protons and electrons
- loses or gains
- loses
Cation
• for metals the name of the cations is the same as the
• Sodium atom forms a sodium cation (Na^+)
• Calcium atoms forms a calcium cation (Ca^2+)
• although their names do not change, it is highly possible that cations have big chemical differences when compared to the metal
• Sodium reacts explosively with water
• Sodium cations are quite non reactive (part of table salt)
- name of the element
Group 1A cations
- the most common cations are those produced by the _____ of valence electrons from metal atoms
- Sodium can lose an electron to become a positively charged sodium ion.
- A sodium ion has an electrical configuration similar to the noble gas neon
- loss
- Sodium can lose an electron to become a positively charged sodium ion.
- A sodium ion has an electrical configuration similar to the noble gas neon
Representing cations
• you can represent the loss of an electron or ionization of the sodium atom by writing the complete
electron configuration of the atom and the ion formed
Group 2a cations
• magnesium atom attains the electron configuration of a neon atom by losing two valence electrons and producing a magnesium cation with a charge of 2+
• The atoms of metals lose the number of electrons necessary to attain the electron configuration of a ________ _____
• 1A metals lose one electron
• 2a metals lose two electrons
Noble gas
Transition metal cations
Transition metal cations
• the charges of cation of the transition metals may vary
• Iron can lose two electrons forming Fe^2+
• Iron can also lose three electrons forming Fe^3+
• Some ions for we by transition metals do not have noble gas electron configurations (ns^2np^6) and are therefore are exceptions to the octet rule
- ions with charges of 3 or greater are uncommon
- Silver does not attain a noble gas configuration
- If silver loses its 5s^1 electron forming a positive ion Ag+ the configuration results in the 4s^24p^6
- With electrons in the highest occupied energy level and all of the orbitals filled is favorable
- This is a pseudo-noble gas configuration
Ok
How do chemists model the valence electrons of metal atoms
Chemists can Model the valence electrons of metal atoms into body centered cubic, face centered cubic, and hexagonal close-packed
Why are alloys more useful than pure metals
Alloys are more useful than our metals because their properties are often superior to those of their component elements
Define ductile and malleable
Ductile means that if you pull it then it will stretch before it breaks
Malleable means that you can hit really hard with something and it will only bend
Why is it possible to bend metals but not Ionic crystals
It is possible to bend metals because they have a sea of flowing electrons that can move around but Ionic crystals don’t have that so you can not bend ionic crystals
Name two widely used alloys and describe their uses
Copper + tin = bronze and steel are both widely used alloys. They can be found in tools, buildings, and many other things
