RAM extension despite lower clock rate buy?

I want to buy RAM and I came across cheap. Although it fits in my laptop, but has a slightly lower clock rate. Here's the data:

Now: 2x 4gb, 2400mhz

Then: 1x16gb, 2133 mhz

Does it make sense to upgrade with it? Or does it even make the laptop slower? What is the ratio between clock rate and gigabyte?

Yes, it will probably make sense, at least if you do not get along with your 8GB now and regularly data must be outsourced.

With more ram, it behaves much like installing an SSD instead of an HDD. The PC can't calculate faster, but it reacts faster because less or less data needs to be reloaded.

Instead of once 18 GB I would have taken 2x8GB not to have to do without the DualChannel mode, through the waiver last the memory accesses longer because instead of 128Bit only 64Bit per access can be loaded.

The clock is lower in 98% of all cases not bad, the PC / notebook adjusts to the lower clock.

There's no relationship to clock rate / gigabyte, because there are two completely different things that you wanted to compare. About the same as if you want to compare whether the trunk volume of a car in relation to the power of the engine in proportion.

Due to the lower clock the PC loses about 1% in speed due to the slower memory accesses. By renouncing dual channel again about 3-8%.

The difference between z.b.

1 x 8GB of RAM and 2 x 4GB of RAM can potentially result in up to 40% performance degradation.

2 x 4 GB of RAM are much faster.

1 x 16 GB RAM? What for? And if 16GB of RAM then 2 x 8GB.

For Intel CPU, the RAM clock is not as relevant as AMD CPUs. The dear fast RAM.

In addition to what bcords and willeswissen64 answered:
Experience has shown that RAM bars of various types can make a system unstable.
Therefore, it is usually recommended to always use exactly the same.

In your case, where you throw out the old two and leave only one inside, that's of course negligible.
But changing from two to one RAM bar also means a performance penalty, since dual-channel operation is no longer possible. (The system can therefore no longer address 2 RAM bars in parallel.)

General Rule: Check the manual of the manufacturer, which RAM-bars are compatible and then take (in your example) 2x8 GB.

Rule of experience: Cheap is that a thing.
Usually, RAM bars become more expensive the older the RAM technology is.
Simply because less of it is produced.
A rule of thumb when buying is therefore always to buy twice as much RAM as you currently need. This is usually cheaper than later retrofit and you have the same built-in RAM bars from the outset and thus a higher stability.

2x4 are always faster.

Dual channel mode.