Cards and Probability

Many questions in Maths Papers look at the probability of selecting a card but many students don't play cards except perhaps on a computer games and don't know the names, values or suits.

 

The Laplace rail demonstration

The Laplace rail demonstration is a piece of scientific equipment used to demonstrate the force exerted on a current-carrying conductor in a magnetic field, illustrating the motor effect and fundamental electromagnetic principles. 

Spirogyra

 Life is beginning in the pond and it is a good time to look at spirogyra and get the students to try and record what they actually see rather than what they think they see.

Food Rewards

 A-Level Psychology: We are what we eat. Does what our mother ate when pregnant affect what we like to eat and does letting kids have food rewards help them in the long term?

Analog Computers

 A Level Computing. Looking at different types of computers, including some analog computers.  Unlike digital computers that use discrete data, they use continuously variable physical quantities, like voltage or mechanical motion, to model and solve problems.

What’s So Special About the Dative Covalent Bond?

A-Level Chemistry: What is the difference between a normal covalent bond and a dative covalent bond. Although the electrons are shown differently in a diagram, there is no difference between them in reality, and in reactions, any of the bonds might be broken.

What’s So Special About the Dative Covalent Bond?

When you first learn about covalent bonding in GCSE Chemistry, it's pretty straightforward: two atoms share a pair of electrons to fill up their outer shells and become more stable. But at A-level, things get juicier. You’re introduced to a slightly more complex version of the covalent bond—the dative covalent bond, also known as a coordinate bond.

So, what is this mysterious bond, and how is it different from the good old ordinary covalent bond? Let’s break it down.

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🧪 The Ordinary Covalent Bond

In a normal covalent bond, each atom provides one electron to the shared pair. Think of it like two friends splitting the bill at a café: one pays for the coffee, the other for the cake. Fair and square.

For example:

• In a molecule of hydrogen (H₂), each hydrogen atom has one electron. They come together and share, forming a bond with a pair of electrons—one from each atom.
• In oxygen gas (O₂), each oxygen shares two electrons, forming a double covalent bond.

This sharing allows both atoms to achieve a stable electron configuration (often the noble gas configuration).

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🎯 Enter the Dative Covalent Bond (Coordinate Bond)

Now imagine a situation where one atom provides both electrons for the bond. This is a dative covalent bond.

It’s like one friend paying for the entire meal while the other friend just turns up and enjoys the food. Generous? Perhaps. But both still get a good time out of it—just like both atoms benefit from the bond.

💬 Key Definition:

A dative covalent bond is a type of covalent bond in which both electrons in the shared pair come from the same atom.

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🌟 Examples of Dative Covalent Bonds

1. Ammonium Ion (NH₄⁺)

• Ammonia (NH₃) has a lone pair of electrons on the nitrogen atom.
• A hydrogen ion (H⁺), which has no electrons, comes along.
• Nitrogen donates both electrons from its lone pair to form a bond with the H⁺.
• The result? An ammonium ion with four N–H bonds—one of which is dative.

✏️ We usually show the dative bond with an arrow pointing from the donor atom:

![N → H⁺]

2. Aluminium Chloride (Al₂Cl₆)

• In its dimer form, one aluminium atom (electron-deficient) accepts a lone pair from a chloride ion.
• This donation creates a dative bond from Cl to Al.

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🧠 So… What’s the Difference Again?

Feature	Ordinary Covalent Bond	Dative Covalent Bond
Electron Contribution	One electron from each atom	Both electrons from one atom
Still Covalent?	✅ Yes	✅ Yes
Representation	Single line (–)	Arrow (→), from donor to acceptor
Example	H₂, O₂, CH₄	NH₄⁺, Al₂Cl₆, H₃O⁺

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🎓 Why Does It Matter?

At A-level, understanding who's donating what in a bond is essential—especially when it comes to:

• Drawing correct dot-and-cross diagrams
• Naming ions and compounds
• Predicting shapes of molecules (VSEPR theory)
• Understanding acid-base behaviour (in Bronsted-Lowry and Lewis terms)

It also appears in:

• Transition metal complexes
• Biological systems (e.g. haemoglobin binding O₂)

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🧪 Summary

Dative covalent bonds are just a special case of covalent bonding, where one atom does all the sharing. It’s still covalent, it still involves shared electrons, but the ownership history of those electrons tells us a lot about chemical reactivity and structure.

Next time you see a lone pair looking for something to bond with—ask yourself: “Could this be a dative bond moment?”

 

Firmware up to date

 Some of the regular jobs using the @pascoscientific sensors is the keep all the firmware up to date and charge or change the batteries so the sensors are ready for action.