PSC315118 Chemical Structures and Properties Flashcards

Comprehensive practice flashcards covering chemical structure and properties, including periodic table trends, material types, bonding models, and hydrocarbon chemistry.

How is the structure of the periodic table determined?

The structure is based on the electron configuration of atoms.

What is the definition of valency in chemical bonding?

Valency is a measure of the number of bonds that an atom can form.

Why do ionic compounds have high melting points and brittleness?

They are modeled as ions arranged in a crystalline lattice structure with strong forces of attraction between oppositely charged ions; distortion of the lattice causes ions of the same charge to repel and shatter the crystal.

How is metallic bonding modeled to explain properties like malleability and conductivity?

Metallic bonding is a regular arrangement of positive ions (cations) made stable by electrostatic forces of attraction between the ions and a sea of delocalised electrons free to move within the structure.

What are allotropes, and what are the two main examples for carbon cited in the text?

Allotropes are forms of the same element that exhibit different physical properties; common examples for carbon are graphite and diamond.

What occurs in a polar covalent bond like the one found in water?

One atom exerts a greater attraction for the bonding electrons than the other, creating a slight negative charge ($\delta-$) on the Oxygen atom and a slight positive charge ($\delta+$) on the Hydrogen atoms.

What is the Octet Rule?

Main-group elements or atoms of low atomic number tend to combine or become ions so that they each have eight electrons in their valence shell, giving them the same electron configuration as a noble gas.

What results from the decrease in atomic size across a period?

Increasing electrostatic attraction between the increasing number of protons in the nucleus and the electrons in the same main shell pulls the outermost electrons closer, reducing the atomic radii.

What is the trend for electronegativity down a group?

Electronegativity generally decreases down a group as electrons are further from the nucleus and are shielded from the attraction by inner shell electrons.

Who discovered that xenon could form chemical compounds in 1962?

Neil Bartlett.

What is a polyatomic ion?

A group of covalently bonded atoms that acts as a single entity and carries an overall charge, such as Carbonate ($CO_3^{2-}$) or Ammonium ($NH_4^+$).

What is the difference between an empirical formula and a molecular formula?

An empirical formula gives the simplest ratio of atoms or ions in a compound, while a molecular formula represents the actual number of atoms in a molecule.

Why can graphite conduct electricity while diamond cannot?

In graphite, each carbon atom is bonded to three others, leaving a delocalised sea of electrons that can move; in diamond, all valence electrons are used in four strong covalent bonds, leaving no free electrons.

What are the characteristics of an addition reaction involving alkenes?

Alkenes undergo rapid addition reactions with halogens ($X_2$), hydrogen ($H_2$), or hydrogen halides ($HX$) across the double bond.

What is the standard laboratory test to distinguish between saturated and unsaturated hydrocarbons?

The bromine water test; brown bromine water will rapidly discolour/go clear if shaken with an unsaturated alkene, but will not react with a saturated alkane without UV light.

What is the definition of an isomer?

Isomers are compounds which have the same molecular formula but have different structural arrangements.

What are the products of the complete combustion of a hydrocarbon like butane ($C_4H_{10}$)?

Carbon dioxide ($CO_2$) and water vapour ($H_2O$).

What determines if a combustion reaction is incomplete?

A limited supply of oxygen or air, which results in products such as carbon monoxide ($CO$) or soot/carbon ($C$).

What is the general formula for Alkanes?

$$C_nH_{2n+2}$$

What is the general formula for Alkenes?

$$C_nH_{2n}$$

What is the general formula for Alkynes?

$$C_nH_{2n-2}$$

What colour does Potassium ($K^+$) produce in a flame test?

Lilac.

What colour does Copper ($Cu^{2+}$) produce in a flame test?

Blue-green.

Why does hydrogen sometimes appear in group 1 and sometimes in group 17?

Like group 1, it has one valence electron and may lose it; however, like group 17 halogens, it can also gain an electron when reacting.

What are the characteristics of covalent network solids?

The whole crystal is one giant macromolecule held together by a continuous linkage of strong covalent bonds, making it very hard with high melting points (e.g., diamond, $SiO_2$).