# 0.3 The periodic table  (Page 3/5)

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Several other trends may be observed across a period such as density, melting points and boiling points. These trends are not as obvious to see as the above trends and often show variations to the general trend.

Electron affinity and electronegativity also show some general trends across periods. Electron affinity can be thought of as how much an element wants electrons. Electron affinity generally increases from left to right across a period. Electronegativity is the tendency of atoms to attract electrons. The higher the electronegativity, the greater the atom attracts electrons. Electronegativity generally increases across a period (from left to right). Electronegativity and electron affinity will be covered in more detail in a later grade.

You may see periodic tables labeled with s-block, p-block, d-block and f-block. This is simply another way to group the elements. When we group elements like this we are simply noting which orbitals are being filled in each block. This method of grouping is not very useful to the work covered at this level.

Using the properties of the groups and the trends that we observe in certain properties (ionization energy, formation of halides and oxides, melting and boiling points, atomic diameter) we can predict the the properties of unknown elements. For example, the properties of the unfamiliar elements Francium (Fr), Barium (Ba), Astatine (At), and Xenon (Xe) can be predicted by knowing their position on the periodic table. Using the periodic table we can say: Francium (Group 1) is an alkali metal, very reactive and needs to lose 1 electron to obtain a full outer energy shell; Barium (Group 2) is an alkali earth metal and needs to lose 2 electrons to achieve stability; Astatine (Group 7) is a halogen, very reactive and needs to gain 1 electron to obtain a full outer energy shell; and Xenon (Group 8) is a noble gas and thus stable due to its full outer energy shell. This is how scientists are able to say what sort of properties the atoms in the last period have. Almost all of the elements in this period do not occur naturally on earth and are made in laboratories. These atoms do not exist for very long (they are very unstable and break apart easily) and so measuring their properties is difficult.

## Exercise: elements in the periodic table

Refer to the elements listed below:

• Lithium ( $\mathrm{Li}$ )
• Chlorine ( $\mathrm{Cl}$ )
• Magnesium ( $\mathrm{Mg}$ )
• Neon ( $\mathrm{Ne}$ )
• Oxygen ( $\mathrm{O}$ )
• Calcium ( $\mathrm{Ca}$ )
• Carbon ( $\mathrm{C}$ )
Which of the elements listed above:
1. belongs to Group 1
2. is a halogen
3. is a noble gas
4. is an alkali metal
5. has an atomic number of 12
6. has 4 neutrons in the nucleus of its atoms
7. contains electrons in the 4th energy level
8. has only one valence electron
9. has all its energy orbitals full
10. will have chemical properties that are most similar
11. will form positive ions

## Ions

In the previous section, we focused our attention on the electron configuration of neutral atoms. In a neutral atom, the number of protons is the same as the number of electrons. But what happens if an atom gains or loses electrons? Does it mean that the atom will still be part of the same element?

#### Questions & Answers

it is the situation where by im a market there is only one supplier and producer of a certain comodity that has no close substitute or competitor
yes
Alhaji
what is demand and supply
Alhaji
what is Economics?
Is the study of human behaviour as a relationship between ends and scares mean which have alternative use
Alhaji
yes
Tawa
what is monopoly
Alhaji
what are the difficultés if retail prix index for calculating thé value of money
Oscar
hmm OK wait
Castino
what is labour
LABOUR is a measure of work done by human being
Blessing
It is all form of human effort use to utilize in production
Alhaji
Why is scarcity a foundermental problem in economics
Alhaji
Why is scarcity a foundermental problem in economics
scarcity occur unbalance demand and supply at this time cost goods increase then inflation very increase
Tesfaye
scarcity is a foundermental problem because its a natural situation and it affects the world at Large.in other words,it's limit in supply relating to deman
Akwosih
'Economics is about making choices in the presence of scarcity"
. 'Economics is about making choices in the presence of scarcity" - Dscuss.
manoj
describe the producer's scarce resources.. I.e land,Labour,capital and enterprise
short in supply
Charles
What are human behaviour?
the rationality in decision making
Charles
how can you describe economic goods in a much better easier way?
any thing that have utility
Charles
what is deman and supply
Demand can be defined as the ability and willingness to buy commodities in a given price of goods and services in a particular period of time
Alasana
supply refers to the ability and willingness to offered commodities for sale in a given price of goods and services in a period of time .
Alasana
Demand can refer to the ability and willingness to purchase a commodity at a giving price and time.
habib
what must the producer do if total costs exceed total revenue
raise price
Nguyen
reduce cost
Charles
scarcity resources sample
land
Charles
what's scarcity
resources short in supply
Charles
hello
scarcity is excess against human wants.
Kennedy
scarcity is limit in supply relating to demand
Akwosih
students
Hamdu
shortge of resources .imbalance of wants to resources .
Hamdu
hlo
Yahya
limitation of supply in relation to their demand for commodity
Prince
what are the two types of economic theory's?
i thick it is microeconomic theory and macroeconomic theory. or it can be normative and positive economic theories.
Deep
yes^
Nguyen
with diagrams show thé change in prices in thé different time period that can result in an increase in demande
define momentary period
Fankam
What is a monopsony?
monopsony is a situation where only one buyer is available in the market
The
And with many sellers?
Allan
oligopsony
The
to be more specific, oligopsony is a situation with many sellers but few buyers
The
Thank you
Allan
Researchers demonstrated that the hippocampus functions in memory processing by creating lesions in the hippocampi of rats, which resulted in ________.
The formulation of new memories is sometimes called ________, and the process of bringing up old memories is called ________.
What makes metals better to use as wires than non-metals? (please link to bonding type)??? HELP