Atomic structure
In this topic, I learnt about the 3 particles that make up an atom.
They are the
1. Protons (charge of +1, relative mass 1)
2. Neutrons (charge of 0, relative mass 1)
3. Electrons (charge of -1, relative mass 1/200)
All these particles are represented as part of the atom in the Atomic model
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| Atomic model |
Parts of the atomic model:
1.Nucleus (Takes up less than 1% of atom, contains protons and neutrons)
2.Shells (Where the neutrons move around)
3.Valence shell (The shell furthest from the nucleus. Involved in chemical bonding.
Types of ions:
- Cations: When an atom loses 1 or more electrons, it becomes a positively charged particle known as a cation.
- Anions: When an atom gains 1 or more electrons, it becomes a negatively charged particle known as a anion.
In chemical symbols:
- Number above: Mass number(total number of electrons and neutrons)
- Number below: Atomic number (total number of Proton)
Isotopes are atoms of the same element but with different number of neutrons. Thus, they differ in physical properties but possess the same chemical properties due to the same number of protons.
Periodic Table
The modern periodic table was invented by a Russian chemist known as Dmitri Mendeleev in 1989.
Facts about the periodic table:
- Sorted by atomic number of elements
- Elements change from metallic to non-metallic as we move across the table
- Most reactive elements are at the sides while least reactive are at the middle
- Elements in the same group have similar chemical properties and have same number of electrons in their valence shells
- Elements in the same period have the same number of shells occupied by electrons
- Elements in group 1 are Alkali metals
- Elements in group 2 are Alkaline Earth metals
- Elements in group 7 are Halogens
- Elements in group 0 Noble gases
- Elements between group 2 and 3 are transition metals
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| Ionic Bonding |
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| Covalent Bonding |
- Ionic bonding: These bonds result from the transfer of electrons from metal atoms to non-metal atoms forming positive and negative bonds. The electrical forces between these oppositely charged ions produce strong ionic bonds.
- Covalent bonding: A covalent bond is formed by the sharing of a pair of atoms between 2 non-metal atoms. Each atom contributes one electron to the bond.
An acid is a substance that only produces hydrogen ions as the only positive ion when it is dissolved in water.
Strong acids:
- Man-made
- Corrosive
- Ionises completely in water to produce high concentration of hydrogen ions
- Good electrical conductor
- Hydrochloric acid and Sulfuric acid
Weak acids
- Naturally occurring
- Used in food and is not corrosive
- Partially ionises in water to produce few hydrogen ions
- Poor electrical conductor
- Citric acid and ethanoic acid
Acids + metals → salt + hydrogen.
Observations:
Observations:
Observations:
Observations:
- Effervescence occurred. Colorless and odorless gas evolved. This gas extinguishes a lighted splint with a pop sound.
- Grey solid dissolves to form a colorless solution.
- Heat liberated.
Observations:
- Effervescence occurred. Colorless and odorless gas evolved. This gas reacts with calcium hydroxide to form a white precipitate.
- White solid dissolves to form a colorless solution.
Observations:
- A colorless solution is formed.
- No gas is evolved.
Strong alkali:
- Base that dissolves completely to produce hydroxide ions.
- Sodium Hydroxide
- Base that dissolves partially to produce few hydroxide ions
- Ammonia
- An acidic oxide is a non-metallic oxide that neutralises a base to form salt and water only
- Reacts with water to form acid solution
- Carbon dioxide
Basic oxide:
- A basic oxide is a metallic oxide that neutralises an acid to form salt and water only
- Reacts with water to form alkali
- Calcium oxide
Neutral oxide:
- A neutral oxide is a non-metallic oxide that shows neither acidic or alkali properties
- Does not react with water
- Carbon monoxide
Amphoteic oxide:
- An ampoteric oxide is a metallic oxide that react with both acid and base to form salt and water only
- Possess acidic and basic property
- Zinc oxide
Acids + bases → salt + water
Observations:
Observations:
Observations:
- A colorless solution is formed.
- No gas is evolved.
Observations:
- A colorless and pungent gas is evolved. This gas turns damp red litmus paper blue.
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| pH scale |
Various indicator can be used to find out the pH of a substance:
Litmus paper
- Acid turns blue litmus paper red
- Alkali turns red litmus paper blue
- Colour change at pH 4
- Used to identify strong acids
- Strong acid turns methyl orange red
- Alkali turns methyl orange yellow
Phenolphthalein
- Used to identify strong alkalis
- Colour change at pH 9
- Strong alkali turns phenolphthalein pink
- Acid makes phenolphthalein remain colourless
- Remains green in neutral solution
- Turns red in strong acid
- Turns violet in strong alkali
Reflections
I felt that term 1 was quite fascinating as when I was young I always assumed that an atom would be a microscopic red round ball, just like Dalton's model. However, I learnt that they are the atom's nucleus with electrons moving at very fast speeds around them. I felt that the topic of electronic structure was quite easy to understand but it was easy to make careless mistakes here and there due to the charges written as 2+ instead of +2. Another topic taught this term is the periodic table and how it relates to atom's electronic charges and chemical properties of them. I feel that Mr Medelev was a genius as he was able to come up with such a handy table for classifying elements according to their various properties, he was also able to predict what kind of elements would be found in the future and deliberately left blanks in the table so that others could add on to his work. This term I got 28.5/45, which was a wasted opportunity as the topics tested were relatively easy to understand.
I felt that term 1 was quite fascinating as when I was young I always assumed that an atom would be a microscopic red round ball, just like Dalton's model. However, I learnt that they are the atom's nucleus with electrons moving at very fast speeds around them. I felt that the topic of electronic structure was quite easy to understand but it was easy to make careless mistakes here and there due to the charges written as 2+ instead of +2. Another topic taught this term is the periodic table and how it relates to atom's electronic charges and chemical properties of them. I feel that Mr Medelev was a genius as he was able to come up with such a handy table for classifying elements according to their various properties, he was also able to predict what kind of elements would be found in the future and deliberately left blanks in the table so that others could add on to his work. This term I got 28.5/45, which was a wasted opportunity as the topics tested were relatively easy to understand.
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