chem - atomic structure and the periodic table

What is an atom

an atom is the smallest part of an element that can exist

What is an element

an element is a substance of only one type of atom

How are the elements listed and approximately how many are there?

they are listed in the periodic table , there are approximately 100

Elements can be classified into two groups based on their properties , what are these groups?

metals and non metals

Elements may combine through chemical reactions to form new products , what are these new substances called?

compounds

What is a compound?

two or more elements combined chemically in a fixed proportions which can be represented by formulae

Do compounds have the same properties as their constituent elements?

no , they have different properties

What is a mixture? Does it have the same chemical properties as its constituent materials?

A mixture consists of two or more elements or compounds not chemically combined together , it does have the same chemical properties

What are the methods though which mixtures can be separated ( there are five ) ? Do these involve chemical reactions

Filtration , crystallisation , simple distillation ,fractional distillation and chromatography they do not involve chemical reactions

Describe and explain simple distillation

simple distillation is used to separate liquid from a solution — the liquid boils off and condenses in the condenser. The thermometer will read the boiling point of the pure liquid . Contrary to evaporation, we get to keep the liquid.

Describe and explain crytallisation/ evaporation

evaporation is a technique for separation of a solid dissolved in a solvent from a solvent(e.g salt from H2O).

the solution is heated until all the solvent evaporates ; the solids stays in the vessel.

crystallisation is similar , but we only remove some of the solvent by evaporation to form a saturated solution ( the one where no more solid can be dissolved). Then. we cool down the solution. As we do it , the solid starts to crystallise , as it becomes less soluble at lower temperatures.The crystals can be collected and separated from the solvent via filtration.

Describe and explain fractional distillation

Fractional distillation is a technique for separation of a mixture of liquids.

It works when liquids have different boiling points.

The apparatus is similar to the one of simple distillation apparatus, with the additional fractionating column placed on top of the heated flask.

The fractionating column contains glass beads. It helps to separate the compounds . In industry, mixtures are repeatedly condensed and vapourised. The column is hot at the bottom and cold at the top . the liquids will condense at different heights of the column.

Describe and explain filtration

Filtration is used to separate an insoluble solid is suspended in a liquid.

the soluble solid(called a residue) gets caught in the filter paper , because the particles are too big to fit through the holes in the paper.

Apparatus: filter paper + funnel

Describe the plum pudding model

The atom is a ball of positive charge with negative election embedded in it.

Describe the Bohr/nuclear model and how it came about

The nuclear model suggests that electrons orbit the nucleus at specific distances ( shells ) it came about from the alpha scattering experiments

Later experiments led to the discovery of smaller positive particles in the nucleus ; what are these particles called

Protons

What did the work of James Chadwick provide evidence for?

The existence of neutrons in the nucleus

What did the work of James Chadwick provide evidence for ?

The existence of neutrons in the nucleus

Describe the structure of an atom

the atom has a small central nucleus ( made up of protons and neutrons) around which there are electrons

State the relative masses and relative charges of the proton neutron and electron

Masses: 1, 1, very small ; Charges 1, 0 , -1 (respectively)

Explain why atoms are electrically neutral

They have the same number of electrons and protons

what is the radius of an atom

0.1nm

What is the radius of a nucleus and what is it compared to that of the atom?

1×10^-14m and 1/10000

What name is given to the number of protons in the nucleus?

atomic number

Atoms of the same element have the same number of which particle in the nucleus?

protons

Where is the majority of mass of an atom

The nucleus

What is the mass number

The total number of protons and neutrons

How does one calculate the number of neutrons using mass number and atomic number?

Subtract the atomic number from the mass number

What is an isotope? Do isotopes of a certain element have the same chemical properties?

Atoms of the same element (same proton number) that have a different number of neutrons.

They have the same chemical properties as they have the same electronic structure.

What is the relative atomic mass?

The average mass value which takes the mass and the abundance of isotopes of an element into account on the scale where the mass of ^12C is 12

What are ions

Charged particles , formed when atoms lose or gain electrons

Compare the properties of metals and non metals

Boiling point :

Metals —> High

Non metals—> low

Conductivity:

Metals —> heat & electricity

Non metals —> Dont conduct heat & electricity apart from graphite

Appearance:

Metals —> shiny

Non metals —> dull

Malleability:

Metals —> yes

Non metals —> brittle

Density :

Metals —> high

Non mentals —> low

Oxides:

Metal —> Basic

Non metal —> acidic

What is formed when a metal reacts with a non metal

Ionic compound (made of + and - ions)

What is formed when a non metal reacts with a non metal

Molecular compound containing covalently bonded atoms

The columns of a periodic table are called

Groups

The rows are the periodic table are called

Periods

Are elements in the same group

May have similar chemical properties, as they have the same number of outer shell electrons

In terms of energy levels (shells) what are the differences between elements of the same period

They have the same number of energy levels

Element group 0 more commonly known as

Noble gases

Early periodic table were incomplete and placed inappropriate groups if what is to be used

Strict order of atomic weights