Chemistry Basics Lecture Notes

Comprehensive practice flashcards reviewing chemistry foundational concepts including atomic structure, periodic table layout, electronic configurations, oxidation-reduction, and chemical reaction types.

What is Organic Chemistry?

A branch of chemistry responsible for studying compounds that contain mainly both carbon atoms and hydrogen atoms.

What is an element?

A pure substance made only of one type of atom, such as $Na$, $Fe$, and $Cl_2$.

Which seven elements exist as diatomic molecules?

$H_2$, $N_2$, $O_2$, $F_2$, $Cl_2$, $Br_2$, and $I_2$.

What are examples of polyatomic molecules mentioned in the lecture?

$O_3$, $P_4$, and $S_8$.

What is an atom and what are its main components?

The smallest particle of a chemical substance. It consists of a positively charged nucleus (containing positively charged protons and neutral neutrons) and negatively charged electrons rotating around the nucleus in energy levels.

What is the atomic number?

The number of protons inside the nucleus or the number of electrons rotating around the nucleus in an electrically neutral atom.

What is the mass number?

The total number of protons and neutrons in an atom.

How is the modern periodic table structured?

It consists of $7$ horizontal periods and $18$ vertical columns.

What are the four main blocks of the modern periodic table?

The $s$, $p$, $d$, and $f$ blocks.

What are the four types of elements classified in the modern periodic table?

Representative elements ($s$ & $p$ block), Main transition elements ($d$ block), Inner transition elements ($f$ block), and Noble elements (inert gas).

Which groups contain representative elements and main transition elements?

Representative elements are from group $1A$ to $7A$. Main transition elements are from group $3B$ to $1B$ (except group $2B$).

How many electrons can occupy an orbital, and what are the electron capacities of the sublevels $s$, $p$, $d$, and $f$?

An orbital is occupied by $2$ electrons only. Sublevel $s$ holds $1:2$ electrons, $p$ holds $1:6$ electrons, $d$ holds $1:10$ electrons, and $f$ holds $1:14$ electrons.

What is the Building-up principle (Aufbau principle)?

Electrons occupy the energy sublevels of lower energy first, followed by the sublevels of higher energy in ascending order: $1s < 2s < 2p < 3s < 3p < 4s < 3d < 4p < 5s < 4d < 5p < 6s < 4f < 5d < 6p < 7s < 5f < 6d < 7p$.

What is Hund's rule?

No pairing of electrons takes place in a given sublevel orbital until each orbital is filled by a single electron.

Why are Chromium ($_{24}Cr$) and Copper ($_{29}Cu$) exceptions to normal electronic configuration rules?

Their outer sublevels are either half-filled or completely filled ($_{24}Cr$: $[_{18}Ar]\text{ }3d^5\text{ }4s^1$; $_{29}Cu$: $[_{18}Ar]\text{ }3d^{10}\text{ }4s^1$), which lowers their energy and makes them more stable.

What is an ion and how do cations and anions differ?

An ion is formed when an atom loses or gains one or more electrons during a chemical reaction. A cation is a positively charged ion ($+ve$) formed by losing electrons, while an anion is a negatively charged ion ($-ve$) formed by gaining electrons.

What is oxidation?

The process by which a substance loses electrons and its oxidation number increases.

What is reduction?

The process by which a substance gains electrons and its oxidation number decreases.

What are oxidizing agents and reducing agents?

An oxidizing agent is the substance that undergoes reduction, and a reducing agent is the substance that undergoes oxidation.

What is a direct combination reaction?

A reaction where two or more substances combine to form one product ($A + B \rightarrow AB$), for example $N_2 + 3H_2 \rightarrow 2NH_3$.

What is a decomposition reaction?

A reaction where one compound breaks down into two or more simpler substances ($AB \rightarrow A + B$), for example $FeCO_3 \rightarrow FeO + CO_2$.

What is a simple substitution reaction?

A reaction where one element replaces another element in a compound ($A + BC \rightarrow AC + B$), for example $Zn + CuSO_4 \rightarrow ZnSO_4 + Cu$.

What is a double substitution reaction?

A reaction where two compounds exchange their ions to form two new compounds ($AB + CD \rightarrow AD + CB$), for example $NaCl + AgNO_3 \rightarrow NaNO_3 + AgCl$.