Questions and Answers
Which of the following is the symbol for Potassium?
What is the correct symbol for Beryllium?
Identify the element that has the symbol 'Ne'.
Which element's symbol is 'Cl'?
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What is the symbol for Oxygen?
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Which of the following is a characteristic of non-metals?
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What defines metalloids?
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Which of these elements is classified as a noble gas?
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Which symbol correctly represents Aluminium?
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Which of the following statements about the symbols of elements is true?
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Which of the following is NOT a characteristic of non-metals?
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What is the primary reason for using two-letter symbols for elements with the same first letter?
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Which of the following elements has a symbol derived from its Latin name?
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What information does the symbol of an element convey?
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How many elements are typically expected to be represented in a compound?
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Which of these compounds is correctly defined based on its elemental composition?
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What does the symbol 'Na' represent in the context of elements?
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What distinguishes pure substances from mixtures?
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What major contribution to chemistry did Jons Jacob Berzelius make?
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Which of the following statements about elements is correct?
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Which of these elements is classified as a metal?
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Which of the following elements was NOT discovered by Berzelius?
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During which century did Jons Jacob Berzelius make his contributions to chemistry?
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Which property is characteristic of metals?
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How many known elements are there today?
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What was one of Berzelius's achievements related to atomic weights?
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What is the classification of the element with the symbol 'Au'?
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Which of the following statements is true about Jons Jacob Berzelius?
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What uniquely characterizes the composition of a compound?
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Which of the following properties is true for all compounds?
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Which example correctly identifies the physical state of a compound at room temperature?
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What is required to separate a compound into its constituent elements?
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What typically occurs during the formation of a compound?
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How do the properties of compounds differ from those of elements?
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What distinguishes a compound from an element?
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Which of the following classifications does not describe elements?
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Which property is true for noble gases?
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What defines an element?
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What indicates that sodium chloride is a compound?
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Which of the following is a characteristic of non-metals?
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Which statement is true about elements?
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How can a compound be defined in terms of composition?
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A pure substance consists of particles of only one ______.
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An ______ is a pure substance that cannot be broken down into simpler substances by any physical or ordinary chemical means.
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A ______ is a substance made up of two or more elements chemically combined together in a fixed ratio.
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The ______of an element is a single-letter or two-letter abbreviation of its full name.
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A ______ formula represents the composition of a molecule of an element or a compound.
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Study Notes
Elements
- Hydrogen, helium, lithium, beryllium, boron, carbon, nitrogen, oxygen, fluorine, neon, sodium, magnesium, aluminium, silicon, phosphorus, sulphur, chlorine, argon, potassium, and calcium are the first twenty elements.
- There are 118 known elements today, out of which 92 occur naturally and the remaining are made by humans.
Classification of Elements
- Elements are classified into:
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Metals: gold, silver, iron, aluminium, and copper are examples of metals.
- They are usually hard solids.
- They have a characteristic shine or lustre.
- They are good conductors of heat and electricity.
- They have high melting and boiling points.
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Non-metals: carbon, hydrogen, oxygen, and nitrogen are examples of non-metals.
- They are either soft solids or gases.
- They do not possess shine or lustre.
- They are bad conductors of heat and electricity.
- They have low melting and boiling points.
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Metalloids: silicon, germanium, arsenic, and antimony are examples of metalloids.
- They have intermediate properties between those of metals and non-metals.
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Noble or Inert Gases: helium, neon, argon, krypton, xenon, and radon are examples of noble or inert gases.
- They do not react chemically with other elements.
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Metals: gold, silver, iron, aluminium, and copper are examples of metals.
Symbols of Elements
- Elements are represented by symbols, which are single-letter or two-letter abbreviations of their full names.
- The present system of allotting symbols to the elements was introduced by J.J. Berzelius.
- The IUPAC approves the names and symbols of new elements.
Compounds
- A compound is a substance made up of two or more elements chemically combined in a fixed ratio.
- Compounds have properties different from those of their constituent elements.
- Examples of compounds include water, sodium chloride (common salt), and sodium hydroxide.
Characteristics of Compounds
- Compounds are made up of two or more elements.
- Compounds are homogeneous, meaning all samples of a compound are identical in composition and have the same properties throughout.
- The properties of a compound are different from those of its constituent elements.
- It is not possible to separate the constituents of a compound by physical means.
- Energy is usually given off or absorbed when a compound is formed.
Difference Between Elements and Compounds
- Elements are made up of only one kind of substance.
- Elements cannot be broken down into simpler substances by chemical means.
- Elements have unique properties.
- Compounds are made up of two or more elements.
- Compounds can be broken down into their constituent elements by chemical means.
- The properties of a compound are different from those of its constituent elements.
Characteristics of Pure Substances
- A pure substance consists of particles of only one kind.
Classification of Elements
- Elements are classified into four categories based on their properties: metals, non-metals, metalloids, and noble or inert gases.
Definition of an Element
- An element is a pure substance that cannot be broken down into simpler substances by any physical or ordinary chemical means.
Symbol of an Element
- An element's symbol is a single-letter or two-letter abbreviation of its full name.
Definition of a Compound
- A compound is a substance made up of two or more elements chemically combined together in a fixed ratio.
Atomic Structure
- An atom is the smallest particle of an element that possesses all the properties of that element.
- Atoms may or may not have independent existence.
Molecular Structure
- A molecule is the smallest particle of an element or a compound that has independent existence.
- Molecules show all the properties of the substance they represent.
Molecular Formula
- A molecular formula represents the composition of a molecule of an element or a compound.
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Description
Learn the names and symbols of the first 20 elements in the periodic table, from Hydrogen to Calcium. Test your knowledge of the chemical symbols and their corresponding elements.